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  • 1.
    Andersson, Magnus
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    A quality process for assessing mathematics in a study programme2018In: Proceedings från 6:e utvecklingskonferensen för Sveriges ingenjörsutbildningar / [ed] Lena Petersson, Kristina Edström, Oskar Gedda, Fredrik Georgsson, Liselott Lycke och Marie Arehag, 2018Conference paper (Refereed)
    Abstract [en]

    We present two methodologies to assess the use of mathematics in a study programme. Firstly, we use a relatively simple methodology to assess how students show their ability to use mathematics in their degree project reports. Secondly, we present a methodology to assess how mathematics is used during a study programme. We have applied the first methodology on the mathematics content in 114 randomly chosen bachelor degree reports from 6 different study programmes within the fields of electrical engineering and computer engineering at KTH. For the 3-year bachelor degree programmes in computer engineering, we find clear deficits in the way students use mathematics in their bachelor degree reports as compared to the other programmes in our study. Through the second methodology, we were able to relate the deficits in the bachelor degree reports to a programme structure where skills in mathematics have not been sufficiently demanded in the engineering courses of the programme. 

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  • 2.
    Azimi-Mousolou, Vahid
    et al.
    Univ Isfahan, Fac Math & Stat, Dept Appl Math & Comp Sci, Esfahan 8174673441, Iran.;Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Bergman, Anders
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Alballova Univ Ctr, Sch Engn Sci.
    Eriksson, Olle
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Pereiro, Manuel
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Thonig, Danny
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Sjoqvist, Erik
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Entanglement duality in spin-spin interactions2022In: Physical Review A: covering atomic, molecular, and optical physics and quantum information, ISSN 2469-9926, E-ISSN 2469-9934, Vol. 106, no 3, article id 032407Article in journal (Refereed)
    Abstract [en]

    We examine entanglement of thermal states for spin-1/2 dimers in external magnetic fields. Entanglement transition in the temperature-magnetic-field plane demonstrates a duality in spin-spin interactions. This identifies a pair of dual categories of symmetric and antisymmetric dimers with each category classified into toric entanglement classes. The entanglement transition line is preserved from each toric entanglement class to its dual toric class. The toric classification is an indication of the topological signature of the entanglement, which bring about topological stability that could be relevant for quantum information processing.

  • 3.
    Azimi-Mousolou, Vahid
    et al.
    Department of Applied Mathematics and Computer Science, Faculty of Mathematics and Statistics, University of Isfahan, Isfahan 81746-73441, Iran; Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden, Box 516.
    Bergman, Anders
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden, Box 516.
    Delin, Anna
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Eriksson, Olle
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden, Box 516.
    Pereiro, Manuel
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden, Box 516.
    Thonig, Danny
    School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden.
    Sjöqvist, Erik
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden, Box 516.
    Transmon probe for quantum characteristics of magnons in antiferromagnets2023In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 108, no 9, article id 094430Article in journal (Refereed)
    Abstract [en]

    The detection of magnons and their quantum properties, especially in antiferromagnetic (AFM) materials, is a substantial step to realize many ambitious advances in the study of nanomagnetism and the development of energy efficient quantum technologies. The recent development of hybrid systems based on superconducting circuits provides the possibility to engineer quantum sensors that exploit different degrees of freedom. Here, we examine the magnon-photon-transmon hybridization based on bipartite AFM materials, which gives rise to an effective coupling between a transmon qubit and magnons in a bipartite AFM. We demonstrate how magnon modes, their chiralities, and quantum properties, such as nonlocality and two-mode magnon entanglement in bipartite AFMs, can be characterized through the Rabi frequency of the superconducting transmon qubit.

  • 4. Bergman, Anders
    et al.
    Hellsvik, Johan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Bessarab, Pavel F.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Univ Iceland, Iceland.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala Univ, Sweden.
    Spin relaxation signature of colossal magnetic anisotropy in platinum atomic chains2016In: Scientific Reports, E-ISSN 2045-2322, Vol. 6, article id 36872Article in journal (Refereed)
    Abstract [en]

    Recent experimental data demonstrate emerging magnetic order in platinum atomically thin nanowires. Furthermore, an unusual form of magnetic anisotropy-colossal magnetic anisotropy (CMA)-was earlier predicted to exist in atomically thin platinum nanowires. Using spin dynamics simulations based on first-principles calculations, we here explore the spin dynamics of atomically thin platinum wires to reveal the spin relaxation signature of colossal magnetic anisotropy, comparing it with other types of anisotropy such as uniaxial magnetic anisotropy (UMA). We find that the CMA alters the spin relaxation process distinctly and, most importantly, causes a large speed-up of the magnetic relaxation compared to uniaxial magnetic anisotropy. The magnetic behavior of the nanowire exhibiting CMA should be possible to identify experimentally at the nanosecond time scale for temperatures below 5 K. This time-scale is accessible in e.g., soft x-ray free electron laser experiments.

  • 5.
    Bergman, Anders
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Skubic, B
    Hellsvik, J
    Nordstrom, L
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Eriksson, O
    Ultrafast switching in a synthetic antiferromagnetic magnetic random-access memory device2011In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 83, no 22Article in journal (Refereed)
    Abstract [en]

    The dynamics of a synthetic antiferromagnet (a metallic trilayer) have been explored and are shown to exhibit ultrafast switching on a time scale of tens of ps. This conclusion is based on first-principles, atomistic spin dynamics simulations. The simulations are performed at finite temperature, as well as at T = 0 K (the macrospin limit), and we observe a marked temperature dependence of the switching phenomenon. It is shown that, to reach very high switching speeds, it is important that the two ferromagnetic components of the synthetic antiferromagnet have oppositely directed external fields to one another. Then a complex collaboration between precession switching of an internal exchange field and the damping switching of the external field occurs, which considerably accelerates the magnetization dynamics. We discuss a possible application of this fast switching as a magnetic random access memory device, which has as a key component intrinsic antiferromagnetic couplings and an applied Oersted field.

  • 6. Bessarab, Pavel F.
    et al.
    Mueller, Gideon P.
    Lobanov, Igor S.
    Rybakov, Filipp N.
    KTH, School of Engineering Sciences (SCI), Physics, Statistical Physics.
    Kiselev, Nikolai S.
    Jonsson, Hannes
    Uzdin, Valery M.
    Blugel, Stefan
    Bergqvist, Lars
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Lifetime of racetrack skyrmions2018In: Scientific Reports, E-ISSN 2045-2322, Vol. 8, article id 3433Article in journal (Refereed)
    Abstract [en]

    The skyrmion racetrack is a promising concept for future information technology. There, binary bits are carried by nanoscale spin swirls-skyrmions-driven along magnetic strips. Stability of the skyrmions is a critical issue for realising this technology. Here we demonstrate that the racetrack skyrmion lifetime can be calculated from first principles as a function of temperature, magnetic field and track width. Our method combines harmonic transition state theory extended to include Goldstone modes, with an atomistic spin Hamiltonian parametrized from density functional theory calculations. We demonstrate that two annihilation mechanisms contribute to the skyrmion stability: At low external magnetic field, escape through the track boundary prevails, but a crossover field exists, above which the collapse in the interior becomes dominant. Considering a Pd/Fe bilayer on an Ir(111) substrate as a well-established model system, the calculated skyrmion lifetime is found to be consistent with reported experimental measurements. Our simulations also show that the Arrhenius pre-exponential factor of escape depends only weakly on the external magnetic field, whereas the pre-exponential factor for collapse is strongly field dependent. Our results open the door for predictive simulations, free from empirical parameters, to aid the design of skyrmion-based information technology.

  • 7.
    Borisov, Vladislav
    et al.
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Kvashnin, Yaroslav O.
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Ntallis, Nikolaos
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Thonig, Danny
    Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Thunström, Patrik
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Pereiro, Manuel
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Bergman, Anders
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Sjöqvist, Erik
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Nordström, Lars
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Eriksson, Olle
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Heisenberg and anisotropic exchange interactions in magnetic materials with correlated electronic structure and significant spin-orbit coupling2021In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 103, no 17, article id 174422Article in journal (Refereed)
    Abstract [en]

    The Dzyaloshinskii-Moriya (DM) interaction, as well as symmetric anisotropic exchange, are important ingredients for stabilizing topologically nontrivial magnetic textures, such as, e.g., skyrmions, merons, and hopfions. These types of textures are currently in focus from a fundamental science perspective and they are also discussed in the context of future spintronics information technology. While the theoretical understanding of the Heisenberg exchange interactions is well developed, it is still a challenge to access, from first principles theory, the DM interaction as well as the symmetric anisotropic exchange, which both require a fully-relativistic treatment of the electronic structure, in magnetic systems where substantial electron-electron correlations are present. Here, we present results of a theoretical framework which allows to compute these interactions in any given system and demonstrate its performance for several selected cases, for both bulk and low-dimensional systems. We address several representative cases, including the bulk systems CoPt and FePt, the B20 compounds MnSi and FeGe as well as the low-dimensional transition metal bilayers Co/Pt(111) andMn/W(001). The effect of electron-electron correlations is analyzed using dynamical mean-field theory on the level of the spin-polarized T -matrix + fluctuating exchange (SPTF) approximation, as regards the strength and character of the isotropic (Heisenberg) and anisotropic (DM) interactions in relation to the underlying electronic structure. Our method can be combined with more advanced techniques for treating correlations, e.g., quantum Monte Carlo and exact diagonalization methods for the impurity solver of dynamical mean-field theory. We find that correlation-induced changes of the DM interaction can be rather significant, with up to fivefold modifications in the most distinctive case.

  • 8.
    Borisov, Vladislav
    et al.
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120, Uppsala, Sweden, Box 516.
    Salehi, Nastaran
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120, Uppsala, Sweden, Box 516.
    Pereiro, Manuel
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120, Uppsala, Sweden, Box 516.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Eriksson, Olle
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120, Uppsala, Sweden, Box 516; Wallenberg Initiative Materials Science for Sustainability, Uppsala University, 75121, Uppsala, Sweden.
    Dzyaloshinskii-Moriya interactions, Néel skyrmions and V4 magnetic clusters in multiferroic lacunar spinel GaV4S82024In: npj Computational Materials, E-ISSN 2057-3960, Vol. 10, no 1, article id 53Article in journal (Refereed)
    Abstract [en]

    Using ab initio density functional theory with static mean-field correlations, we calculate the Heisenberg and Dzyaloshinskii-Moriya interactions (DMI) for an atomistic spin Hamiltonian for the lacunar spinel, GaV4S8. The parameters describing these interactions are used in atomistic spin dynamics and micromagnetic simulations. The magnetic properties of the lacunar spinel GaV4S8, a material well-known from experiment to host magnetic skyrmions of Néel character, are simulated with these ab initio calculated parameters. The Dzyaloshinskii-Moriya contribution to the micromagnetic energy is a sum of two Lifshitz invariants, supporting the formation of Néel skyrmions and its symmetry agrees with what is usually expected for C3ν-symmetric systems. There are several conclusions one may draw from this work. One concerns the quantum nature of the magnetism, where we show that the precise magnetic state of the V4 cluster is crucial for understanding quantitatively the magnetic phase diagram. In particular, we demonstrate that a distributed-moment state of each V4 cluster explains well a variety of properties of GaV4S8, such as the band gap, observed Curie temperature and especially the stability of Néel skyrmions in the experimentally relevant temperature and magnetic-field range. In addition, we find that electronic correlations change visibly the calculated value of the DMI.

  • 9.
    Borisov, Vladislav
    et al.
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Xu, Qichen
    KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Ntallis, Nikolaos
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Clulow, Rebecca
    Uppsala Univ, Dept Chem, Box 538, SE-75121 Uppsala, Sweden..
    Shtender, Vitalii
    Uppsala Univ, Dept Chem, Box 538, SE-75121 Uppsala, Sweden..
    Cedervall, Johan
    Stockholm Univ, Dept Mat & Environm Chem, SE-10691 Stockholm, Sweden..
    Sahlberg, Martin
    Uppsala Univ, Dept Chem, Box 538, SE-75121 Uppsala, Sweden..
    Wikfeldt, Kjartan Thor
    KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for High Performance Computing, PDC.
    Thonig, Danny
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Pereiro, Manuel
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Bergman, Anders
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Delin, Anna
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Biotechnology (BIO), Centres, Albanova VinnExcellence Center for Protein Technology, ProNova. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Eriksson, Olle
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Örebro Univ, Sch Sci & Technol, SE-70182 Örebro, Sweden..
    Tuning skyrmions in B20 compounds by 4d and 5d doping2022In: Physical Review Materials, E-ISSN 2475-9953, Vol. 6, no 8, article id 084401Article in journal (Refereed)
    Abstract [en]

    Skyrmion stabilization in novel magnetic systems with the B20 crystal structure is reported here, primarily based on theoretical results. The focus is on the effect of alloying on the 3d sublattice of the B20 structure by substitution of heavier 4d and 5d elements, with the ambition to tune the spin-orbit coupling and its influence on magnetic interactions. State-of-the-art methods based on density functional theory are used to calculate both isotropic and anisotropic exchange interactions. Significant enhancement of the Dzyaloshinskii-Moriya interaction is reported for 5d-doped FeSi and CoSi, accompanied by a large modification of the spin stiffness and spiralization. Micromagnetic simulations coupled to atomistic spin-dynamics and ab initio magnetic interactions reveal the spin-spiral nature of the magnetic ground state and field-induced skyrmions for all these systems. Especially small skyrmions similar to 50 nm are predicted for Co0.75Os0.25Si, compared to similar to 148 nm for Fe0.75Co0.25Si. Convex-hull analysis suggests that all B20 compounds considered here are structurally stable at elevated temperatures and should be possible to synthesize. This prediction is confirmed experimentally by synthesis and structural analysis of the Ru-doped CoSi systems discussed here, both in powder and in single-crystal forms.

  • 10.
    Borlenghi, Simone
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Boman, Magnus
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Software and Computer systems, SCS. RISE SICS, Electrum 229, SE-16429 Kista, Sweden..
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Modeling reservoir computing with the discrete nonlinear Schrodinger equation2018In: Physical review. E, ISSN 2470-0045, E-ISSN 2470-0053, Vol. 98, no 5, article id 052101Article in journal (Refereed)
    Abstract [en]

    We formulate, using the discrete nonlinear Schrodinger equation (DNLS), a general approach to encode and process information based on reservoir computing. Reservoir computing is a promising avenue for realizing neuromorphic computing devices. In such computing systems, training is performed only at the output level by adjusting the output from the reservoir with respect to a target signal. In our formulation, the reservoir can be an arbitrary physical system, driven out of thermal equilibrium by an external driving. The DNLS is a general oscillator model with broad application in physics, and we argue that our approach is completely general and does not depend on the physical realization of the reservoir. The driving, which encodes the object to be recognized, acts as a thermodynamic force, one for each node in the reservoir. Currents associated with these thermodynamic forces in turn encode the output signal from the reservoir. As an example, we consider numerically the problem of supervised learning for pattern recognition, using as a reservoir a network of nonlinear oscillators.

  • 11.
    Borlenghi, Simone
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Delin, Anna
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Stochastic Thermodynamics of Oscillators' Networks2018In: Entropy, E-ISSN 1099-4300, Vol. 20, no 12, article id 992Article in journal (Refereed)
    Abstract [en]

    We apply the stochastic thermodynamics formalism to describe the dynamics of systems of complex Langevin and Fokker-Planck equations. We provide in particular a simple and general recipe to calculate thermodynamical currents, dissipated and propagating heat for networks of nonlinear oscillators. By using the Hodge decomposition of thermodynamical forces and fluxes, we derive a formula for entropy production that generalises the notion of non-potential forces and makes transparent the breaking of detailed balance and of time reversal symmetry for states arbitrarily far from equilibrium. Our formalism is then applied to describe the off-equilibrium thermodynamics of a few examples, notably a continuum ferromagnet, a network of classical spin-oscillators and the Frenkel-Kontorova model of nano friction.

  • 12.
    Borlenghi, Simone
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Uppsala University, Sweden.
    Iubini, Stefano
    Lepri, Stefano
    Bergqvist, Lars
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Uppsala University, Sweden.
    Fransson, Jonas
    Coherent energy transport in classical nonlinear oscillators: An analogy with the Josephson effect2015In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 91, no 4, article id 040102Article in journal (Refereed)
    Abstract [en]

    By means of a simple theoretical model and numerical simulations, we demonstrate the presence of persistent energy currents in a lattice of classical nonlinear oscillators with uniform temperature and chemical potential. In analogy with the well-known Josephson effect, the currents are proportional to the sine of the phase differences between the oscillators. Our results elucidate general aspects of nonequilibrium thermodynamics and point towards a way to practically control transport phenomena in a large class of systems. We apply the model to describe the phase-controlled spin-wave current in a bilayer nanopillar.

  • 13.
    Borlenghi, Simone
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Uppsala University, Sweden.
    Iubini, Stefano
    Lepri, Stefano
    Chico, Jonathan
    Bergqvist, Lars
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. Uppsala University, Sweden.
    Fransson, Jonas
    Energy and magnetization transport in nonequilibrium macrospin systems2015In: Physical Review E. Statistical, Nonlinear, and Soft Matter Physics, ISSN 1539-3755, E-ISSN 1550-2376, Vol. 92, no 1, article id 012116Article in journal (Refereed)
    Abstract [en]

    We investigate numerically the magnetization dynamics of an array of nanodisks interacting through the magnetodipolar coupling. In the presence of a temperature gradient, the chain reaches a nonequilibrium steady state where energy and magnetization currents propagate. This effect can be described as the flow of energy and particle currents in an off-equilibrium discrete nonlinear Schrodinger (DNLS) equation. This model makes transparent the transport properties of the system and allows for a precise definition of temperature and chemical potential for a precessing spin. The present study proposes a setup for the spin-Seebeck effect, and shows that its qualitative features can be captured by a general oscillator-chain model.

  • 14.
    Borlenghi, Simone
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Lepri, Stefano
    Bergqvist, Lars
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Thermomagnonic diode: Rectification of energy and magnetization currents2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 89, no 5, p. 054428-Article in journal (Refereed)
    Abstract [en]

    We investigate the dynamics of two coupled macrospins connected to thermal baths at different temperatures. The system behaves like a diode which allows the propagation of energy and magnetization currents in one direction only. This effect is described by a simple model of two coupled nonlinear oscillators interacting with two independent reservoirs. It is shown that the rectification phenomenon can be interpreted as a a stochastic phase synchronization of the two spin oscillators. A brief comparison with realistic micromagnetic simulations is presented. This new effect yields promising opportunities in spin caloritronics and nanophononic devices.

  • 15. Borlenghi, Simone
    et al.
    Mahani, M. Reza
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala University, Sweden.
    Fransson, Jonas
    Nanoscale control of heat and spin conduction in artificial spin chains2016In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 94, no 13, article id 134419Article in journal (Refereed)
    Abstract [en]

    We describe a mechanism to control the energy and magnetization currents in an artificial spin chain, consisting of an array of permalloy nanodisks coupled through a magnetodipolar interaction. The chain is kept out of equilibrium by two thermal baths with different temperatures connected to its ends, which control the current propagation. Transport is enhanced by applying a uniform radio-frequency pump field resonating with some of the spin-wave modes of the chain. Moreover, the two currents can be controlled independently by tuning the static field applied on the chain. Thus we describe two effective means for the independent control of coupled currents and the enhancement of thermal and spin-wave conductivity in a realistic magnonics device, suggesting that similar effects could be observed in a large class of nonlinear oscillating systems.

  • 16. Borlenghi, Simone
    et al.
    Mahani, Mohammad Reza
    KTH, School of Engineering Sciences (SCI), Applied Physics.
    Fangohr, Hans
    Franchin, M.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala Univ, Sweden.
    Fransson, Jonas
    Micromagnetic simulations of spin-torque driven magnetization dynamics with spatially resolved spin transport and magnetization texture2017In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 9, article id 094428Article in journal (Refereed)
    Abstract [en]

    We present a simple and fast method to simulate spin-torque driven magnetization dynamics in nanopillar spin-valve structures. The approach is based on the coupling between a spin transport code based on random matrix theory and a micromagnetics finite-elements software. In this way the spatial dependence of both spin transport and magnetization dynamics is properly taken into account. Our results are compared with experiments. The excitation of the spin-wave modes, including the threshold current for steady-state magnetization precession and the nonlinear frequency shift of the modes are reproduced correctly. The giant magneto resistance effect and the magnetization switching also agree with experiment. The similarities with recently described spin-caloritronics devices are also discussed.

  • 17.
    Borlenghi, Simone
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Wang, Weiwei
    Fangohr, Hans
    Bergqvist, Lars
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Designing a Spin-Seebeck Diode2014In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 112, no 4, p. 047203-Article in journal (Refereed)
    Abstract [en]

    Using micromagnetic simulations, we have investigated spin dynamics in a spin-valve bilayer in the presence of a thermal gradient. The direction and the intensity of the gradient allow us to excite the spin wave modes of each layer selectively. This permits us to synchronize the magnetization precession of the two layers and to rectify the flows of energy and magnetization through the system. Our study yields promising opportunities for applications in spin caloritronics and nanophononics devices.

  • 18.
    Cao, Weimin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Matsushita, Taishi
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Theoretical investigation of sulfur adsorption on FE (100)2009In: TMS 2009 138TH ANNUAL MEETING & EXHIBITION - SUPPLEMENTAL PROCEEDINGS, VOL 3: GENERAL PAPER SELECTIONS, WARRENDALE: MINERALS, METALS & MATERIALS SOC , 2009, p. 523-528Conference paper (Refereed)
    Abstract [en]

    The electronic and structural properties of atomic sulfur adsorbed on the iron surface (100) are examined by using density functional theory (DFT). The sulfur coverage is considered from a quarter of one monolayer (ML) to a full monolayer, and the adsorption energy and work function are calculated for three different adsorption sites of sulfur. Our calculated results indicate that the most likely site for S adsorption is the hollow site on Fe (100), which is agreement with experiment. In addition, at 1 ML coverage, the work function increased after the S adsorption on the Fe (100) surface, which implies that charge transfer from the surface to sulfur has taken place. The results are in agreement with previous theoretical work.

  • 19.
    Cao, Weimin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Delin, Anna
    Seetharaman, Sesadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Coverage dependence of sulfur adsorption on Fe(100): Density functional calculationsIn: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235XArticle in journal (Refereed)
  • 20.
    Cao, Weimin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Calculation of Oxygen and Sulfur Average Velocity on the Iron Surface: A Two-dimensional Gas Model Study2010In: Steel Research International, ISSN 1611-3683, Vol. 81, no 11, p. 949-952Article in journal (Refereed)
    Abstract [en]

    In the present work, a two-dimensional (2D) gas model is derived and used to simulate the average velocity of individual atoms of the surface active elements oxygen and sulfur on the Fe(100) surface. The average velocity of oxygen and sulfur atoms was found to be related to the vibration frequencies and minimal energy barrier. The calculated results are based on data from density functional calculations combined with thermodynamics and statistical physics. The calculated average velocity of oxygen on the Fe (100) is lower than that of sulphur. This is because of the stronger interaction between oxygen and the first iron layer. We conclude that our simple 2D gas model may be useful for simulating and understanding the complex interfacial phenomena in the steelmaking refining process from an atomic point of view.

  • 21.
    Cao, Weimin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Materials Process Science.
    Effect of electronic structure and magnetism on S adsorption on Fe (100) from first principlesIn: Journal of Physical Chemistry A, ISSN 1089-5639, E-ISSN 1520-5215Article in journal (Other academic)
  • 22.
    Cardias, Ramon
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. Instituto de Física, Universidade Federal Fluminense, 24210-346 Niterói, RJ, Brazil.
    Silva, Jhonatan dos Santos
    Faculdade de Física, Universidade Federal do Pará, 66075-110 Belém, PA, Brazil; Instituto Federal de Educação, Ciência e Tecnologia do Pará, 68250-000 Óbidos, PA, Brazil.
    Bergman, Anders
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
    Szilva, Attila
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
    Kvashnin, Yaroslav O.
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
    Fransson, Jonas
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
    Klautau, Angela B.
    Faculdade de Física, Universidade Federal do Pará, 66075-110 Belém, PA, Brazil; Departamento de Física da Universidade de Aveiro, 3810-183 Aveiro, Portugal.
    Eriksson, Olle
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden; Wallenberg Initiative Materials Science for Sustainability (WISE), Uppsala University Box 516, SE-75120 Uppsala, Sweden.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Wallenberg Initiative Materials Science for Sustainability (WISE).
    Nordström, Lars
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
    Unraveling the connection between high-order magnetic interactions and local-to-global spin Hamiltonian in noncollinear magnetic dimers2023In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 108, no 22, article id 224408Article in journal (Refereed)
    Abstract [en]

    A spin Hamiltonian that characterizes interatomic interactions between spin moments is highly valuable in predicting and comprehending the magnetic properties of materials. Here, we explore a method for explicitly calculating interatomic exchange interactions in noncollinear configurations of magnetic materials considering only a bilinear spin Hamiltonian in a local scenario. Based on density-functional theory calculations of dimers adsorbed on metallic surfaces, and with a focus on the Dzyaloshinskii-Moriya interaction (DMI) which is essential for stabilizing chiral noncollinear magnetic states, we discuss the interpretation of the DMI when decomposed into microscopic electron and spin densities and currents. We clarify the distinct origins of spin currents induced in the system and their connection to the DMI. In addition, we reveal how noncollinearity affects the usual DMI, which is solely induced by spin-orbit coupling, and DMI-like interactions brought about by noncollinearity. We explain how the dependence of the DMI on the magnetic configuration establishes a connection between high-order magnetic interactions, enabling the transition from a local to a global spin Hamiltonian.

  • 23.
    Cardias, Ramon
    et al.
    KTH. Univ Paris Saclay, CEA, CNRS, SPEC, F-91191 Gif Sur Yvette, France..
    Szilva, Attila
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Bergman, Anders
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Kvashnin, Yaroslav
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Fransson, Jonas
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Streib, Simon
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Katsnelson, Mikhail I.
    Radboud Univ Nijmegen, Inst Mol & Mat, Heyendaalseweg 135, NL-6525 AJ Nijmegen, Netherlands..
    Thonig, Danny
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Örebro Univ, Sch Sci & Technol, Fakultetsgatan 1, SE-70281 Örebro, Sweden..
    Klautau, Angela Burlamaqui
    Univ Fed Para, Fac Fis, BR-66075110 Belem, PA, Brazil..
    Eriksson, Olle
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden.;Örebro Univ, Sch Sci & Technol, Fakultetsgatan 1, SE-70281 Örebro, Sweden..
    Nordstrom, Lars
    Uppsala Univ, Dept Phys & Astron, Box 516, SE-75120 Uppsala, Sweden..
    Comment on "Proper and improper chiral magnetic interactions"2022In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 105, no 2, article id 026401Article in journal (Refereed)
    Abstract [en]

    In a recent paper by dos Santos Dias et al. [Phys. Rev. B 103, L140408 (2021)], a critique of earlier works analyzing low-energy spin Hamiltonians is put forth. To be precise, it is the large noncollinear contributions to the Dzyaloshinskii-Moriya interaction (DMI) that is the main concern of dos Santos Dias et al. In this Comment, we clarify the microscopic mechanisms for the large DMI that can be found in noncollinear magnets. Furthermore, we outline the complementary nature of the different parametrizations of a spin Hamiltonian, with strengths and weaknesses of both approaches. Specifically, we stress the physical insight in the interpretation of the DMI, when decomposed in microscopic electron and spin densities and currents.

  • 24.
    Chareev, Dmitriy A.
    et al.
    Institute of Experimental Mineralogy (IEM RAS), 142432 Chernogolovka, Moscow Region, Russia; Kazan Federal University, 18 Kremlyovskaya St., 420008 Kazan, Russia; Ural Federal University, 620002 Ekaterinburg, Russia.
    Khan, Md Ezaz Hasan
    University of Doha for Science and Technology, 24449 Doha, P.O. Box 24449, Qatar.
    Karmakar, Debjani
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
    Nekrasov, Aleksey N.
    Institute of Experimental Mineralogy (IEM RAS), 142432 Chernogolovka, Moscow Region, Russia.
    Nickolsky, Maximilian S.
    Institute of Geology of Ore Deposits (IGEM RAS), 35, Staromonetnyi per., 119017 Moscow, Russia.
    Eriksson, Olle
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden; School of Science and Technology, Örebro University, SE-701 82 Örebro, Sweden.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Vasiliev, Alexander N.
    Lomonosov Moscow State University, 119991 Moscow, Russia; National University of Science and Technology “MISiS”, 119049 Moscow, Russia.
    Abdel-Hafiez, Mahmoud
    University of Doha for Science and Technology, 24449 Doha, P.O. Box 24449, Qatar; Department of Physics and Astronomy, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
    Stable Sulfuric Vapor Transport and Liquid Sulfur Growth on Transition Metal Dichalcogenides2023In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 23, no 4, p. 2287-2294Article in journal (Refereed)
    Abstract [en]

    Transition metal dichalcogenides (TMDs) are an emergent class of low-dimensional materials with growing applications in the field of nanoelectronics. However, efficient methods for synthesizing large monocrystals of these systems are still lacking. Here, we describe an efficient synthetic route for a large number of TMDs that were obtained in quartz glass ampoules by sulfuric vapor transport and liquid sulfur. Unlike the sublimation technique, the metal enters the gas phase in the form of molecules, hence containing a greater amount of sulfur than the growing crystal. We have investigated the physical properties for a selection of these crystals and compared them to state-of-the-art findings reported in the literature. The acquired electronic properties features demonstrate the overall high quality of single crystals grown in this work as exemplified by CoS2, ReS2, NbS2, and TaS2. This new approach to synthesize high-quality TMD single crystals can alleviate many material quality concerns and is suitable for emerging electronic devices.

  • 25. Chico, Jonathan
    et al.
    Etz, Corina
    Bergqvist, Lars
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics.
    Eriksson, Olle
    Fransson, Jonas
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics. Uppsala Univ, Sweden.
    Bergman, Anders
    Thermally driven domain-wall motion in Fe on W(110)2014In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 90, no 1, p. 014434-Article in journal (Refereed)
    Abstract [en]

    It has recently been shown that domain walls (DWs) in ferromagnets can be moved in the presence of thermal gradients. In this work we study the motion of narrow domain walls in low-dimensional systems when subjected to thermal gradients. The system chosen is a monolayer of Fe on W(110) which is known to exhibit a large anisotropy while having a soft exchange, resulting in a very narrow domain wall. The study is performed by means of atomistic spin dynamics simulations coupled to first-principles calculations. By subjecting this system to thermal gradients we observe a temperature-dependent movement of the domain wall. The thermal gradient always makes the domain wall move towards the hotter region of the sample with a velocity proportional to the gradient. Our material specific study is complemented by model simulations to discern the interplay between the thermal gradient, magnetic anisotropy, and the exchange interaction and shows that the larger DW velocities are found for materials with broader domain-wall width. The relatively slow DW motion of the Fe/W(110) system is hence primarily caused by its narrow domain-wall width, which results from its large magnetic anisotropy and soft exchange.

  • 26.
    Delin, Anna
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    First-principles calculations of the II-VI semiconductor beta-HgS: Metal or semiconductor2002In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 65, no 15Article in journal (Refereed)
    Abstract [en]

    Relativistic all-electron full-potential first-principles calculations have been performed in order to study the symmetry of the energy levels around the valence band maximum in the zinc blende II-VI semiconductors beta-HgS, HgSe, and HgTe. It is demonstrated that in general, an inverted band-structure does not necessarily lead to a zero fundamental energy gap for systems with zinc blende symmetry. Specifically, beta-HgS is found to have at the same time an inverted band structure, and a small, slightly indirect, fundamental energy gap. Possibly, the energy levels around the valence band maximum order differently in each of these systems.

  • 27.
    Delin, Anna
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Kluner, T.
    Excitation spectra and ground-state properties from density-functional theory for the inverted band-structure systems beta-HgS, HgSe, and HgTe2002In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 66, no 3Article in journal (Refereed)
    Abstract [en]

    We have performed a systematic density-functional study of the mercury chalcogenide compounds beta-HgS, HgSe, and HgTe using an all-electron full-potential linear muffin-tin orbital method. We find that, in the zinc-blende structure, both HgSe and HgTe are semimetals whereas beta-HgS has a small spin-orbit-induced band gap. Our calculated relativistic photoemission and inverse photoemission spectra reproduce very well the most recently measured spectra, as do also our theoretical optical spectra. In contrast to the normal situation, we find that the local density approximation to the density functional gives calculated equilibrium volumes in much better agreement with experiment than does the generalized gradient corrected functional. We also address the problem of treating relativistic p electrons with methods based on a scalar-relativistic basis set and show that the effect is rather small for the present systems.

  • 28.
    Delin, Anna
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Tosatti, E
    Emerging magnetism in platinum nanowires2004In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 566, p. 262-267Article in journal (Refereed)
    Abstract [en]

    We have investigated infinitely long, monostrand Pt nanowires theoretically, and found that they exhibit Hund's rule magnetism. We find a spin moment of 0.6 mu(B) per atom, at the equilibrium bond length. Its magnetic moment increases with stretching. The origin of the wire magnetism is analyzed and its effect on the conductance through the wire is discussed.

  • 29.
    Delin, Anna
    et al.
    KTH, Superseded Departments (pre-2005), Materials Science and Engineering.
    Tosatti, E.
    The electronic structure of 4d transition-metal monatomic wires2004In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 16, no 45, p. 8061-8074Article in journal (Refereed)
    Abstract [en]

    Monatomic nanowires of the nonmagnetic transition metals Ru, Rh, and Pd have been studied theoretically, using first-principles computational techniques, in order to investigate the possible onset of magnetism in these nanosystems. Our fully relativistic spin-polarized all-electron density functional calculations reveal the onset of Hund's rule magnetism in nanowires of all three metals, with mean-field moments of 1.1, 0.3, and 0.7 mu(B), respectively, at the equilibrium bond length. An analysis of the band structures indicates that the nanocontact superparamagnetic state suggested by our calculations should affect the ballistic conductance between tips made of Ru, Rh or Pd, leading to possible temperature and magnetic field dependent conductance.

  • 30.
    Delin, Anna
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Tosatti, E.
    Weht, R.
    Delin, Tosatti, and Weht Reply2006In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 96, no 7Article in journal (Refereed)
  • 31.
    Delin, Anna
    et al.
    ICTP, Trieste, Italy.
    Tosatti, Erio
    ICTP, Trieste, Italy.
    Weht, Ruben
    Comis Nacl Energia Atom, Dept Fis, RA-1650 San Martin, Argentina.
    Magnetism in atomic-size palladium contacts and nanowires2004In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 92, no 5, p. 057201-572014Article in journal (Refereed)
    Abstract [en]

    Palladium (Pd) nanowires, that exhibit Hund's rule magnetism are investigated. A spin moment of 0.7μB per atom is found in long, monostrand nanowires. The predicted moment is about 0.3μB per nanowire atom for short, monostrand nanowires between bulk leads. Results show that a coaxial (6,1) nanowire was nonmagnetic in nature.

  • 32. Durrenfeld, P.
    et al.
    Gerhard, F.
    Chico, J.
    Dumas, R. K.
    Ranjbar, M.
    Bergman, A.
    Bergqvist, Lars
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala University, Sweden.
    Gould, C.
    Molenkamp, L. W.
    Åkerman, Johan
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. University of Gothenburg, Sweden; NanOsc AB, Sweden.
    Tunable damping, saturation magnetization, and exchange stiffness of half-Heusler NiMnSb thin films2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 21, article id 214424Article in journal (Refereed)
    Abstract [en]

    The half-metallic half-Heusler alloy NiMnSb is a promising candidate for applications in spintronic devices due to its low magnetic damping and its rich anisotropies. Here we use ferromagnetic resonance (FMR) measurements and calculations from first principles to investigate how the composition of the epitaxially grown NiMnSb influences the magnetodynamic properties of saturation magnetization M-S, Gilbert damping alpha, and exchange stiffness A. M-S and A are shown to have a maximum for stoichiometric composition, while the Gilbert damping is minimum. We find excellent quantitative agreement between theory and experiment for M-S and alpha. The calculated A shows the same trend as the experimental data but has a larger magnitude. In addition to the unique in-plane anisotropy of the material, these tunabilities of the magnetodynamic properties can be taken advantage of when employing NiMnSb films in magnonic devices.

  • 33.
    Elgammal, Karim
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, Superseded Departments (pre-2005), Materials Science and Engineering. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala University.
    Adsorption of carbon dioxide and water molecules on graphene on top of silica substrates: dispersion corrected density functional calculationsManuscript (preprint) (Other academic)
    Abstract [en]

    We report on systematic computational studies of carbon dioxide and water molecule adsorption on graphene, with the graphene layer deposited on top of a substrate. Specifically, we address the influence of cristobalite and quartz substrates, i.e. two different types of silicon dioxide. The computations are based on density functional theory (DFT), with a nonempirical nonlocal van der Waals density functional included to account for dispersion forces.We calculate the binding energies and equilibrium positions of the molecules, as well as charge transfer and how the charge density of the graphene layer changes due to the interactions with the substrate and the molecules. The molecule-graphene bonding distances are found to be in the range 3.3-3.4 Å, and the graphene-substrate bonding distances around 3.6 Å. These values are slightly larger than what we have found previously, using an empirical expression for the van der Waals density functional. At the same time, the values for the binding energies are increased, compared to what we have obtained in a previous study. We find, in all cases, a net electron transfer from the adsorbed molecule to the graphene+substrate system. For quartz, the total charge transfer is between 0.1 and 0.2 electrons per adsorbed molecule. For cristobalite, it is only about a tenth of that. Our findings are consistent with earlier calculations as well as experimental data.

  • 34.
    Elgammal, Karim
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics, Material Physics, MF.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, Superseded Departments (pre-2005), Materials Science and Engineering. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala University.
    Graphene adhesion on surfaces: a van der Waals density functional studyManuscript (preprint) (Other academic)
    Abstract [en]

    We present a van der Waals density functional (vdW-DF) calculations study of graphene adhesion to different types of substrates with different surface conditions. The study expands to both metal and semiconductor substrates with different surface endings. All substrate surfaces were the 111 surfaces where they have hexagonal lattice parameters perfectly matching with the graphene's. Adsorption geometries, energies, bader charges, dipole moments and electronic structure in terms of density of states are investigated. The results are showing a general agrement with both experimental results as well as theoritical findings done with similar setup. The results reveal that the degree of adhesive of graphene to different surfaces can affect the electronic structure of graphene ending in having different applications when designing graphene in building nano-electronic devices.

  • 35.
    Elgammal, Karim
    et al.
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Hugosson, Håkan W.
    Smith, Anderson D.
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits. Chalmers Institute of Technology, Sweden.
    Råsander, Mikael
    Bergqvist, Lars
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala University, Sweden.
    Density functional calculations of graphene-based humidity and carbon dioxide sensors: effect of silica and sapphire substrates2017In: Surface Science, ISSN 0039-6028, E-ISSN 1879-2758, Vol. 663, p. 23-30Article in journal (Refereed)
    Abstract [en]

    We present dispersion-corrected density functional calculations of water and carbon dioxide molecules adsorption on graphene residing on silica and sapphire substrates. The equilibrium positions and bonding distances for the molecules are determined. Water is found to prefer the hollow site in the center of the graphene hexagon, whereas carbon dioxide prefers sites bridging carbon-carbon bonds as well as sites directly on top of carbon atoms. The energy differences between different sites are however minute - typically just a few tenths of a millielectronvolt. Overall, the molecule-graphene bonding distances are found to be in the range 3.1-3.3 (A) over circle. The carbon dioxide binding energy to graphene is found to be almost twice that of the water binding energy (around 0.17 eV compared to around 0.09 eV). The present results compare well with previous calculations, where available. Using charge density differences, we also qualitatively illustrate the effect of the different substrates and molecules on the electronic structure of the graphene sheet.

  • 36.
    Elgammal, Karim
    et al.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Hugosson, Håkan W.
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Smith, Anderson D.
    KTH, School of Information and Communication Technology (ICT), Integrated Devices and Circuits.
    Råsander, Mikael
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF.
    Bergqvist, Lars
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala University.
    Density functional theory calculations of graphene-based humidity and carbon dioxide sensors: effect of silica and sapphire substratesManuscript (preprint) (Other academic)
  • 37.
    Fan, Xuge
    et al.
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Elgammal, Karim
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Smith, Anderson D.
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Östling, Mikael
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. KTH, Centres, SeRC - Swedish e-Science Research Centre. Department of Physics and Astronomy, Materials Theory Division, Uppsala University, Box 516, SE-75120 Uppsala, Sweden.
    Lemme, Max C.
    KTH, School of Information and Communication Technology (ICT), Electronics, Integrated devices and circuits. Department of Electronic Devices, RWTH Aachen University, 52074 Aachen, Germany.
    Niklaus, Frank
    KTH, School of Electrical Engineering (EES), Micro and Nanosystems.
    Humidity and CO2 gas sensing properties of double-layer graphene2018In: Carbon, ISSN 0008-6223, E-ISSN 1873-3891, Vol. 127, p. 576-587Article in journal (Refereed)
    Abstract [en]

    Graphene has interesting gas sensing properties with strong responses of the graphene resistance when exposed to gases. However, the resistance response of double-layer graphene when exposed to humidity and gasses has not yet been characterized and understood. In this paper we study the resistance response of double-layer graphene when exposed to humidity and CO2, respectively. The measured response and recovery times of the graphene resistance to humidity are on the order of several hundred milliseconds. For relative humidity levels of less than ~ 3% RH, the resistance of double-layer graphene is not significantly influenced by the humidity variation. We use such a low humidity atmosphere to investigate the resistance response of double-layer graphene that is exposed to pure CO2 gas, showing a consistent response and recovery behaviour. The resistance of the double-layer graphene decreases linearly with increase of the concentration of pure CO2 gas. Density functional theory simulations indicate that double-layer graphene has a weaker gas response compared to single-layer graphene, which is in agreement with our experimental data. Our investigations contribute to improved understanding of the humidity and CO2 gas sensing properties of double-layer graphene which is important for realizing viable graphene-based gas sensors in the future.

  • 38. George, S.
    et al.
    Kadas, K.
    Jönsson, P. E.
    Muscas, G.
    Magnus, F.
    Eriksson, O.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering. KTH, Centres, SeRC - Swedish e-Science Research Centre. Uppsala Univ, Dept Phys & Astron, Box 516, S-75120 Uppsala, Sweden.
    Andersson, G.
    Local structure in amorphous Sm x Co 1-x: a combined experimental and theoretical study2020In: Journal of Materials Science, ISSN 0022-2461, E-ISSN 1573-4803, Vol. 55, no 26, p. 12488-12498Article in journal (Refereed)
  • 39.
    Hasan, Md Nur
    et al.
    Department of Chemical and Biological Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, SaltLake, Kolkata 700 106, India.
    Bharati, Ritadip
    School of Physical Sciences, National Institute of Science Education and Research HBNI, Jatni - 752050, Odisha, India.
    Hellsvik, Johan
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for High Performance Computing, PDC.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Pal, Samir Kumar
    Department of Chemical and Biological Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, SaltLake, Kolkata 700 106, India.
    Bergman, Anders
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Sharma, Shivalika
    Asia Pacific Center for Theoretical Physics, Pohang 37673, Republic of Korea.
    Di Marco, Igor
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden; Asia Pacific Center for Theoretical Physics, Pohang 37673, Republic of Korea; Department of Physics, Pohang University of Science and Technology, Pohang 37673, Republic of Korea.
    Pereiro, Manuel
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Thunström, Patrik
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Oppeneer, Peter M.
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Eriksson, Olle
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Karmakar, Debjani
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden; Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
    Magnetism in A V3Sb5 (A=Cs, Rb, and K): Origin and Consequences for the Strongly Correlated Phases2023In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 131, no 19, article id 196702Article in journal (Refereed)
    Abstract [en]

    The V-based kagome systems AV3Sb5 (A=Cs, Rb, and K) are unique by virtue of the intricate interplay of nontrivial electronic structure, topology, and intriguing fermiology, rendering them to be a playground of many mutually dependent exotic phases like charge-order and superconductivity. Despite numerous recent studies, the interconnection of magnetism and other complex collective phenomena in these systems has yet not arrived at any conclusion. Using first-principles tools, we demonstrate that their electronic structures, complex fermiologies and phonon dispersions are strongly influenced by the interplay of dynamic electron correlations, nontrivial spin-polarization and spin-orbit coupling. An investigation of the first-principles-derived intersite magnetic exchanges with the complementary analysis of q dependence of the electronic response functions and the electron-phonon coupling indicate that the system conforms as a frustrated spin cluster, where the occurrence of the charge-order phase is intimately related to the mechanism of electron-phonon coupling, rather than the Fermi-surface nesting.

  • 40.
    Hasan, Md. Nur
    et al.
    Department of Chemical, Biological and Macromolecular Sciences S. N. Bose National Centre for Basic Sciences Block JD, Sector‐III, SaltLake Kolkata 700 106 India.
    Sorgenfrei, Felix
    Department of Physics and Astronomy Uppsala University Box 516 Uppsala SE‐75120 Sweden.
    Pan, Nivedita
    Department of Chemical, Biological and Macromolecular Sciences S. N. Bose National Centre for Basic Sciences Block JD, Sector‐III, SaltLake Kolkata 700 106 India.
    Phuyal, Dibya
    Department of Applied Physics KTH Royal Institute of Technology Stockholm SE‐106 91 Sweden.
    Abdel‐Hafiez, Mahmoud
    Department of Physics and Astronomy Uppsala University Box 516 Uppsala SE‐75120 Sweden.
    Pal, Samir Kumar
    Department of Chemical, Biological and Macromolecular Sciences S. N. Bose National Centre for Basic Sciences Block JD, Sector‐III, SaltLake Kolkata 700 106 India.
    Delin, Anna
    KTH, Centres, SeRC - Swedish e-Science Research Centre. KTH, School of Engineering Sciences (SCI), Applied Physics.
    Thunström, Patrik
    Department of Physics and Astronomy Uppsala University Box 516 Uppsala SE‐75120 Sweden.
    Sarma, D. D.
    Solid State and Structural Chemistry Unit Indian Institute of Science Bengaluru 560012 India;CSIR‐National Institute for Interdisciplinary Science and Technology (CSIR‐NIIST) Industrial Estate P.O. Pappanamcode Thiruvananthapuram 695019 India.
    Eriksson, Olle
    Department of Physics and Astronomy Uppsala University Box 516 Uppsala SE‐75120 Sweden;School of Science and Technology Örebro University Örebro S‐701 82 Sweden.
    Karmakar, Debjani
    Department of Physics and Astronomy Uppsala University Box 516 Uppsala SE‐75120 Sweden;Technical Physics Division Bhabha Atomic Research Centre Mumbai 400085 India.
    Re‐Dichalcogenides: Resolving Conflicts of Their Structure–Property Relationship2022In: Advanced Physics Research, ISSN 2751-1200, Vol. 1, no 1, p. 2200010-2200010, article id 2200010Article in journal (Refereed)
  • 41.
    Hellsvik, Johan
    et al.
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory. KTH, Centres, Nordic Institute for Theoretical Physics NORDITA.
    Thonig, Danny
    Modin, Klas
    Iusan, Diana
    Bergman, Anders
    Eriksson, Olle
    Bergqvist, Lars
    Delin, Anna
    General method for atomistic spin-lattice dynamics with first-principles accuracy2019In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, no 10, article id 104302Article in journal (Refereed)
    Abstract [en]

    We present a computationally efficient and general first-principles based method for spin-lattice simulations for solids and clusters. The method is based on a coupling of atomistic spin dynamics and molecular dynamics simulations, expressed through a spin-lattice Hamiltonian, where the bilinear magnetic term is expanded up to second order in displacement. The effect of first-order spin-lattice coupling on the magnon and phonon dispersion in bcc Fe is reported as an example, and we observe good agreement with previous simulations. We also illustrate the coupled spin-lattice dynamics method on a more conceptual level, by exploring dissipation-free spin and lattice motion of small magnetic clusters (a dimer, trimer, and tetramer). The method discussed here opens the door for a quantitative description and understanding of the microscopic origin of many fundamental phenomena of contemporary interest, such as ultrafast demagnetization, magnetocalorics, and spincaloritronics.

  • 42.
    Hugosson, Håkan Wilhelm
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Cao, Weimin
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Seetharaman, Seshadri
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
    Sulfur- and Oxygen-Induced Alterations of the Iron (001) Surface Magnetism and Work Function: A Theoretical Study2013In: The Journal of Physical Chemistry C, ISSN 1932-7447, E-ISSN 1932-7455, Vol. 117, no 12, p. 6161-6171Article in journal (Refereed)
    Abstract [en]

    The electronic structure and magnetic properties of atomic sulfur and oxygen adsorbed on the iron (001) surface are examined using density functional theory (DFT). The sulfur/oxygen coverage is considered from a quarter of one monolayer (ML) to a full monolayer. The work function change, magnetic properties, and density of states are determined and compared. We find that the work function increases with sulfur coverage in agreement with experiment. We also find that sulfur interacts strongly with the surface layer and that the magnetic moment of the Fe surface decreases as the sulfur coverage increases. In the case of oxygen adsorption, we find that the magnetic moment of the surface Fe atoms instead increases. We show that the difference in surface magnetic moment between sulfur adsorption and oxygen adsorption can be simply explained combining the Slater-Pauling rigid band model linking d-occupation and magnetic moment with an electronegativity argument. Moreover, the work function of the Fe surface as a function of oxygen coverage is found to be very sensitive to overlayer arrangement, here seen in the cases of 0.5 ML c(2 x 2) and 0.5 ML p(2 x 1). This is shown to result from large differences in the surface dipole moment change induced by the oxygen adsorption in the two different overlayer arrangements.

  • 43.
    Huttmann, Felix
    et al.
    Univ Cologne, Inst Phys 2, Zulpicher Str 77, D-50937 Cologne, Germany..
    Rothenbach, Nico
    Univ Duisburg Essen, Fak Phys, Lotharstr 1, D-47057 Duisburg, Germany.;Ctr Nanointegrat Duisburg Essen CENIDE, Lotharstr 1, D-47057 Duisburg, Germany..
    Kraus, Stefan
    Univ Cologne, Inst Phys 2, Zulpicher Str 77, D-50937 Cologne, Germany..
    Ollefs, Katharina
    Univ Duisburg Essen, Fak Phys, Lotharstr 1, D-47057 Duisburg, Germany.;Ctr Nanointegrat Duisburg Essen CENIDE, Lotharstr 1, D-47057 Duisburg, Germany..
    Arruda, Lucas M.
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Bernien, Matthias
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Thonig, Danny
    Uppsala Univ, Dept Phys & Astron, Mat Theory, SE-75120 Uppsala, Sweden..
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Fransson, Jonas
    Uppsala Univ, Dept Phys & Astron, Mat Theory, SE-75120 Uppsala, Sweden..
    Kummer, Kurt
    European Synchrotron Radiat Facil, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France..
    Brookes, Nicholas B.
    European Synchrotron Radiat Facil, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France..
    Eriksson, Olle
    Uppsala Univ, Dept Phys & Astron, Mat Theory, SE-75120 Uppsala, Sweden.;Orebro Univ, Sch Sci & Technol, SE-70182 Orebro, Sweden..
    Kuch, Wolfgang
    Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195 Berlin, Germany..
    Michely, Thomas
    Univ Cologne, Inst Phys 2, Zulpicher Str 77, D-50937 Cologne, Germany..
    Wende, Heiko
    Univ Duisburg Essen, Fak Phys, Lotharstr 1, D-47057 Duisburg, Germany.;Ctr Nanointegrat Duisburg Essen CENIDE, Lotharstr 1, D-47057 Duisburg, Germany..
    Europium Cyclooctatetraene Nanowire Carpets: A Low-Dimensional, Organometallic, and Ferromagnetic Insulator2019In: Journal of Physical Chemistry Letters, ISSN 1948-7185, E-ISSN 1948-7185, Vol. 10, no 5, p. 911-917Article in journal (Refereed)
    Abstract [en]

    We investigate the magnetic and electronic properties of europium cyclooctatetraene (EuCot) nanowires by means of low-temperature X-ray magnetic circular dichroism (XMCD) and scanning tunneling microscopy (STM) and spectroscopy (STS). The EuCot nanowires are prepared in situ on a graphene surface. STS measurements identify EuCot as an insulator with a minority band gap of 2.3 eV. By means of Eu M-5,M-4 edge XMCD, orbital and spin magnetic moments of (-0.1 +/- 0.3)mu(B) and (+7.0 +/- 0.6)mu(B), respectively, were determined. Field-dependent measurements of the XMCD signal at the Eu M-5 edge show hysteresis for grazing X-ray incidence at 5 K, thus confirming EuCot as a ferromagnetic material. Our density functional theory calculations reproduce the experimentally observed minority band gap. Modeling the experimental results theoretically, we find that the effective interatomic exchange interaction between Eu atoms is on the order of millielectronvolts, that magnetocrystalline anisotropy energy is roughly half as big, and that dipolar energy is approximately ten times lower.

  • 44.
    Högfeldt, Anna-Karin
    et al.
    KTH, School of Industrial Engineering and Management (ITM), Learning, Learning in Stem.
    Andersson, Magnus
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Berglund, Per
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Industrial Biotechnology.
    Bergman, Margareta
    KTH, School of Industrial Engineering and Management (ITM), Learning, Learning in Stem.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Edström, Kristina
    KTH, School of Industrial Engineering and Management (ITM), Learning, Learning in Stem.
    Geschwind, Lars
    KTH, School of Industrial Engineering and Management (ITM), Learning, Learning in Stem.
    Grillner, Katja
    KTH, School of Architecture and the Built Environment (ABE), Architecture.
    Håkansson, Anne
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Software and Computer systems, SCS.
    Kari, Leif
    KTH, School of Engineering Sciences (SCI), Engineering Mechanics, Fluid Mechanics and Engineering Acoustics.
    Karlsson, Sigbritt
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Polymeric Materials.
    Lilliesköld, Joakim
    KTH, School of Electrical Engineering and Computer Science (EECS), Computer Science, Network and Systems Engineering.
    Nilsson, Mats
    KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Biomedical Engineering and Health Systems, Medical Imaging.
    Pears, Arnold
    KTH, School of Industrial Engineering and Management (ITM), Learning, Learning in Stem.
    Pedagogisk meritering på KTH - Samarbete, excellens och utbildningsinnovation2019In: Bidrag från 7:e Utvecklingskonferensen för Sveriges ingenjörsutbildningar / [ed] Lennart Petterson och Karin Bolldén, Luleå: Luleå University of Technology, 2019, p. 76-81Conference paper (Refereed)
    Abstract [sv]

    Detta bidrag beskriver och analyserar förberedelsefasen inför implementeringen av ett högskolepedagogiskt excellensprogram vid Kungliga Tekniska Högskolan, KTH. Programmet syftar till att ytterligare stärka värdet av pedagogiska meriter och samtidigt bidra till lärosätets fortsatta och fördjupade utveckling av utbildningarna och organisationen. De tydligaste riskerna som har identifierats med befintliga pedagogiska meriteringsmodeller är att de kan skapa ett A- och B-lag (mellan en karriär som forskare och en karriär som lärare). Dessutom är det ofta oklart hur personer som har utnämnts till excellenta lärare ska kunna bidra till organisationens och utbildningens utveckling ur ett kortsiktigt såväl som ett långsiktigt perspektiv. En tydlig svaghet med befintliga pedagogiska meriteringsmodeller är att de inte explicit nog ger emfas till aktivt och relevant utvecklingsarbete, utan fokuserar på egenhändigt skrivna pedagogiska portföljer som sällan är framtidsinriktade. KTH:s högskolepedagogiska excellensprogram siktar på att försöka möta dessa risker och svagheter. KTH har, alltjämt sedan det nationella obligatoriet om 15 hp Högskolepedagogik infördes, kvarhållit detta obligatorium. Stora satsningar har gjorts på den högskolepedagogiska verksamheten. Ett gediget utbud av fortbildningsmöjligheter samt arenor för nätverkande har utvecklats. Samtidigt råder svagheter i systemet gällande prövande och tillvaratagande av pedagogisk skicklighet, och det är tydligt att KTH behöver ytterligare utveckling i området. Författarna menar också att i och med att de utmaningar vi står inför gällande pedagogisk meritering ser relativt lika ut vid landets lärosäten, bör ett stärkt nationellt samarbete och nätverkande inom landets ingenjörsutbildningar främjas inom området. Artikelförfattarna representerar KTH:s övergripande ledning, utbildningsledning samt ledningen för den högskolepedagogiska verksamheten.

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  • 45.
    Iubini, Stefano
    et al.
    CNR, Ist Sistemi Complessi, Via Madonna Piano 10, I-50019 Sesto Fiorentino, Italy.;Univ Padua, Dipartimento Fis & Astron, Via F Marzolo 8, I-35131 Padua, Italy..
    Borlenghi, Simone
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Lepri, Stefano
    CNR, Ist Sistemi Complessi, Via Madonna Piano 10, I-50019 Sesto Fiorentino, Italy.;Ist Nazl Fis Nucl, Via G Sansone 1, I-50019 Sesto Fiorentino, Italy..
    Piazza, Francesco
    CNRS, UPR 4301, CBM, Rue C Sadron, F-45071 Orleans, France.;Univ Orleans, F-45071 Orleans, France..
    Dephasing-Assisted Macrospin Transport2020In: Entropy, E-ISSN 1099-4300, Vol. 22, no 2, article id 210Article in journal (Refereed)
    Abstract [en]

    Transport phenomena are ubiquitous in physics, and it is generally understood that the environmental disorder and noise deteriorates the transfer of excitations. There are, however, cases in which transport can be enhanced by fluctuations. In the present work, we show, by means of micromagnetics simulations, that transport efficiency in a chain of classical macrospins can be greatly increased by an optimal level of dephasing noise. We also demonstrate the same effect in a simplified model, the dissipative Discrete Nonlinear Schrodinger equation, subject to phase noise. Our results point towards the realization of a large class of magnonics and spintronics devices, where disorder and noise can be used to enhance spin-dependent transport efficiency.

  • 46. Joyce, J. J.
    et al.
    Wills, J. M.
    Durakiewicz, T.
    Butterfield, M. T.
    Guziewicz, E.
    Moore, D. P.
    Sarrao, J. L.
    Morales, L. A.
    Arko, A. J.
    Eriksson, O.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Graham, K. S.
    Dual nature of the 5f electrons in plutonium materials2006In: Physica. B, Condensed matter, ISSN 0921-4526, E-ISSN 1873-2135, Vol. 378-80, p. 920-924Article in journal (Refereed)
    Abstract [en]

    The electronic structure of select Pu materials is examined by means of photoemission (PES) and model calculations. We present the first photoemission results and electronic structure calculations for the material PuIn3. Results for Pu materials, including the cubic delta-phase metal and the superconductor PuCoGa5, give indication of the 5f electrons exhibiting both localized and itinerant character. These new results for PuIn3 place this compounds also in the 5f dual nature category. The dual nature of the Pu 5f electrons demarks the boundary between localized and itinerant 5f character in the actinides. The photoemission data for delta-Pu, PuIn3 and PuCoGa5 are compared against model calculations. The calculations are a mixed level model (MLM) which is a multi-electron extension of the generalized gradient approximation. Using the MLM, one obtains good agreement for the volume and total energy minimum with 4 of 5 Pu 5f electrons localized. The calculations also agree well with the PES spectra. Other computational schemes and interpretations are also reviewed.

  • 47. Kanchana, V.
    et al.
    Vaitheeswaran, G.
    Alouani, M.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    Electronic structure and x-ray magnetic circular dichroism of Sr2FeMoO6: Ab initio calculations2007In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 75, no 22Article in journal (Refereed)
    Abstract [en]

    Theoretical investigations of the electronic structure, x-ray absorption, and x-ray magnetic circular dichroism (XMCD) at the Fe L-2,L-3 and Mo L-2,L-3 edges of Sr2FeMoO6 are carried out by means of the generalized gradient approximation. The magnetic coupling between Fe and Mo is found to be antiparallel, which gives direct confirmation of ferrimagnetic ordering and settles controversies existing between the earlier experimental reports. This is also confirmed by our good agreement of the Mo L-2,L-3 edges with experiment. Using our theoretical spectra, we recalculate the spin and orbital magnetic moments by means of the XMCD sum rules and compare the results with a direct self-consistent calculation and experiment.

  • 48. Kanchana, V.
    et al.
    Vaitheeswaran, G.
    Svane, A.
    Delin, Anna
    KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering, Applied Material Physics.
    First-principles study of elastic properties of CeO2, ThO2 and PoO22006In: Journal of Physics: Condensed Matter, ISSN 0953-8984, E-ISSN 1361-648X, Vol. 18, no 42, p. 9615-9624Article in journal (Refereed)
    Abstract [en]

    Using first-principles density functional calculations, the structural and elastic properties of fluorite type oxides CeO2, ThO2 and PoO2 were studied by means of the full-potential linear muffin-tin orbital method. Calculations were performed within the local density approximation (LDA) as well as generalized gradient approximation (GGA) to the exchange correlation potential. The calculated equilibrium lattice constants and bulk moduli are in good agreement with the experimental results, as are the computed elastic constants for CeO2 and ThO2. For PoO2 this is the first quantitative theoretical prediction of the ground state properties, and it still awaits experimental confirmation. The calculations find PoO2 to be a semiconductor with an indirect band gap and elastic constants similar in magnitude to those of CeO2 and ThO2.

  • 49.
    Karmakar, Debjani
    et al.
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden; Technical Physics Division, Bhabha Atomic Research Centre, Mumbai 400085, India.
    Pereiro, Manuel
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Hasan, Md Nur
    Department of Chemical and Biological Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, SaltLake, Kolkata 700 106, India.
    Bharati, Ritadip
    School of Physical Sciences, National Institute of Science Education and Research, Homi Bhabha National Institute (HBNI), Jatni, 752050 Odisha, India.
    Hellsvik, Johan
    KTH, School of Engineering Sciences (SCI), Physics, Condensed Matter Theory. KTH, School of Electrical Engineering and Computer Science (EECS), Centres, Centre for High Performance Computing, PDC.
    Delin, Anna
    KTH, School of Engineering Sciences (SCI), Applied Physics, Materials and Nanophysics. KTH, Centres, SeRC - Swedish e-Science Research Centre.
    Pal, Samir Kumar
    Department of Chemical and Biological Sciences, S. N. Bose National Centre for Basic Sciences, Block JD, Sector-III, SaltLake, Kolkata 700 106, India.
    Bergman, Anders
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Sharma, Shivalika
    Asia Pacific Center for Theoretical Physics, Pohang 37673, Republic of Korea.
    Di Marco, Igor
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden; Asia Pacific Center for Theoretical Physics, Pohang 37673, Republic of Korea; Department of Physics, Pohang University of Science and Technology, Pohang 37673, Republic of Korea.
    Thunström, Patrik
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Oppeneer, Peter M.
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Eriksson, Olle
    Department of Physics and Astronomy, Uppsala University, Box 516, SE-751 20 Uppsala, Sweden.
    Magnetism in A V3Sb5 (A=Cs, Rb, K): Complex landscape of dynamical magnetic textures2023In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 108, no 17, article id 174413Article in journal (Refereed)
    Abstract [en]

    We have investigated the dynamical magnetic properties of the V-based kagome stibnite compounds by combining the ab initio-extracted magnetic parameters of a spin-Hamiltonian, like inter-site exchange parameters, magnetocrystalline anisotropy and site projected magnetic moments, with full-fledged simulations of atomistic spin- dynamics. Our calculations reveal that, in addition to a ferromagnetic order along the [001] direction, the system hosts a complex landscape of magnetic configurations comprised of commensurate and incommensurate spin spirals along the [010] direction. The presence of such chiral magnetic textures may be the key toward solving the mystery about the origin of the experimentally observed inherent breaking of the C6 rotational, mirror, and the time-reversal symmetry.

  • 50. Keshavarz, S.
    et al.
    Kvashnin, Y. O.
    Di Marco, I.
    Delin, Anna
    KTH, School of Information and Communication Technology (ICT), Materials- and Nano Physics, Material Physics, MF. Uppsala University, Sweden.
    Katsnelson, M. I.
    Lichtenstein, A. I.
    Eriksson, O.
    Layer-resolved magnetic exchange interactions of surfaces of late 3d elements: Effects of electronic correlations2015In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 16, article id 165129Article in journal (Refereed)
    Abstract [en]

    We present the results of an ab initio study of the magnetic properties of Fe, Co, and Ni surfaces. In particular, we discuss their electronic structure and magnetic exchange interactions (J(ij)), as obtained bymeans of a combination of density functional theory and dynamical mean-field theory. All studied systems have a pronounced tendency to ferromagnetism both for bulk and surface atoms. The presence of narrowband surface states is shown to enhance the magnetic moment as well as the exchange couplings. The most interesting results were obtained for the Fe surface where the atoms have a tendency to couple antiferromagnetically with each other. This interaction is relatively small when compared to interlayer ferromagnetic interaction, and it depends strongly on the lattice parameter. Local correlation effects are shown to lead to strong changes of the overall shape of the spectral functions. However, they seem not to play a decisive role in the overall picture of magnetic couplings studied here. We have also investigated the influence of correlations on the spin and orbital moments of bulklike and surface atoms. We found that dynamical correlations in general lead to enhanced values of the orbital moment.

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