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Pankratova, M., Miranda, I. P., Thonig, D., Pereiro, M., Sjöqvist, E., Delin, A., . . . Bergman, A. (2024). Coupled atomistic spin-lattice simulations of ultrafast demagnetization in 3d ferromagnets. Scientific Reports, 14(1), Article ID 8138.
Open this publication in new window or tab >>Coupled atomistic spin-lattice simulations of ultrafast demagnetization in 3d ferromagnets
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2024 (English)In: Scientific Reports, E-ISSN 2045-2322, Vol. 14, no 1, article id 8138Article in journal (Refereed) Published
Abstract [en]

Despite decades of research, the role of the lattice and its coupling to the magnetisation during ultrafast demagnetisation processes is still not fully understood. Here we report on studies of both explicit and implicit lattice effects on laser induced ultrafast demagnetisation of bcc Fe and fcc Co. We do this using atomistic spin- and lattice dynamics simulations following a heat-conserving three-temperature model. We show that this type of Langevin-based simulation is able to reproduce observed trends of the ultrafast magnetization dynamics of fcc Co and bcc Fe. The parameters used in our models are all obtained from electronic structure theory, with the exception of the lattice dynamics damping term, where a range of parameters were investigated. It was found that while the explicit spin-lattice coupling in the studied systems does not impact the demagnetisation process notably, the lattice damping has a large influence on the details of the magnetization dynamics. The dynamics of Fe and Co following the absorption of a femtosecond laser pulse are compared with previous results for Ni and similarities and differences in the materials’ behavior are analysed. For all elements investigated so far with this model, we obtain a linear relationship between the value of the maximally demagnetized state and the fluence of the laser pulse, which is in agreement with experiments. Moreover, we demonstrate that the demagnetization amplitude is largest for Ni and smallest for Co. This holds over a wide range of the reported electron-phonon couplings, and this demagnetization trend is in agreement with recent experiments.

Place, publisher, year, edition, pages
Springer Nature, 2024
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-345756 (URN)10.1038/s41598-024-58662-y (DOI)001198141000015 ()38584162 (PubMedID)2-s2.0-85189824720 (Scopus ID)
Note

QC 20240418

Available from: 2024-04-18 Created: 2024-04-18 Last updated: 2024-04-29Bibliographically approved
Borisov, V., Salehi, N., Pereiro, M., Delin, A. & Eriksson, O. (2024). Dzyaloshinskii-Moriya interactions, Néel skyrmions and V4 magnetic clusters in multiferroic lacunar spinel GaV4S8. npj Computational Materials, 10(1), Article ID 53.
Open this publication in new window or tab >>Dzyaloshinskii-Moriya interactions, Néel skyrmions and V4 magnetic clusters in multiferroic lacunar spinel GaV4S8
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2024 (English)In: npj Computational Materials, E-ISSN 2057-3960, Vol. 10, no 1, article id 53Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
Springer Nature, 2024
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-344795 (URN)10.1038/s41524-024-01232-7 (DOI)001185607200001 ()2-s2.0-85187790487 (Scopus ID)
Note

QC 20240408

Available from: 2024-03-28 Created: 2024-03-28 Last updated: 2024-04-08Bibliographically approved
Xu, Q., Shen, Z., Pereiro, M., Sjöqvist, E., Herman, P., Eriksson, O. & Delin, A. (2023). Genetic-tunneling driven energy optimizer for spin systems. Communications Physics, 6(1), Article ID 239.
Open this publication in new window or tab >>Genetic-tunneling driven energy optimizer for spin systems
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2023 (English)In: Communications Physics, E-ISSN 2399-3650, Vol. 6, no 1, article id 239Article in journal (Refereed) Published
Abstract [en]

Finding the ground state of complex many-body systems, such as magnetic materials containing topological textures, like skyrmions, is a fundamental and long-standing problem. We present here a genetic-tunneling-driven variance-controlled optimization method, that efficiently identifies the ground state of two-dimensional skyrmionic systems. The approach combines a local energy-minimizer backend and a metaheuristic global search frontend. The method is shown to perform significantly better than simulated annealing. Specifically, we demonstrate that for the Pd/Fe/Ir(111) system, our method correctly and efficiently identifies the experimentally observed spin spiral geometry, skyrmion lattice and ferromagnetic ground states as a function of the external magnetic field. To our knowledge, no other optimization method has until now succeeded in doing this. We envision that our findings will pave the way for evolutionary computing in mapping out phase diagrams for spin systems in general.

Place, publisher, year, edition, pages
Springer Nature, 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-336301 (URN)10.1038/s42005-023-01360-4 (DOI)2-s2.0-85169699856 (Scopus ID)
Note

QC 20230913

Available from: 2023-09-13 Created: 2023-09-13 Last updated: 2024-05-07Bibliographically approved
Lu, Z., Miranda, I. P., Streib, S., Pereiro, M., Sjöqvist, E., Eriksson, O., . . . Delin, A. (2023). Influence of nonlocal damping on magnon properties of ferromagnets. Physical Review B, 108(1), Article ID 014433.
Open this publication in new window or tab >>Influence of nonlocal damping on magnon properties of ferromagnets
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2023 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 108, no 1, article id 014433Article in journal (Refereed) Published
Abstract [en]

We study the influence of nonlocal damping on the magnon properties of Fe, Co, Ni, and Fe1-xCox (x=30%,50%) alloys. The Gilbert damping parameter is typically considered as a local scalar both in experiment and in theoretical modeling. However, recent works have revealed that Gilbert damping is a nonlocal quantity that allows for energy dissipation between atomic sites. With the Gilbert damping parameters calculated from a state-of-the-art real-space electronic structure method, magnon lifetimes are evaluated from spin dynamics and linear response, where a good agreement is found between these two methods. It is found that nonlocal damping affects the magnon lifetimes in different ways depending on the system. Specifically, we find that in Fe, Co, and Ni, the nonlocal damping decreases the magnon lifetimes, while in Fe70Co30 and Fe50Co50 an opposite, nonlocal damping effect is observed, and our data show that it is much stronger in the former.

Place, publisher, year, edition, pages
American Physical Society (APS), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-335299 (URN)10.1103/PhysRevB.108.014433 (DOI)001122919500002 ()2-s2.0-85166950613 (Scopus ID)
Note

QC 20230905

Available from: 2023-09-05 Created: 2023-09-05 Last updated: 2024-01-16Bibliographically approved
Hasan, M. N., Bharati, R., Hellsvik, J., Delin, A., Pal, S. K., Bergman, A., . . . Karmakar, D. (2023). Magnetism in A V3Sb5 (A=Cs, Rb, and K): Origin and Consequences for the Strongly Correlated Phases. Physical Review Letters, 131(19), Article ID 196702.
Open this publication in new window or tab >>Magnetism in A V3Sb5 (A=Cs, Rb, and K): Origin and Consequences for the Strongly Correlated Phases
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2023 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 131, no 19, article id 196702Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Physical Society (APS), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-340287 (URN)10.1103/PhysRevLett.131.196702 (DOI)001155751900003 ()38000423 (PubMedID)2-s2.0-85177068595 (Scopus ID)
Note

QC 20231201

Available from: 2023-12-01 Created: 2023-12-01 Last updated: 2024-02-29Bibliographically approved
Karmakar, D., Pereiro, M., Hasan, M. N., Bharati, R., Hellsvik, J., Delin, A., . . . Eriksson, O. (2023). Magnetism in A V3Sb5 (A=Cs, Rb, K): Complex landscape of dynamical magnetic textures. Physical Review B, 108(17), Article ID 174413.
Open this publication in new window or tab >>Magnetism in A V3Sb5 (A=Cs, Rb, K): Complex landscape of dynamical magnetic textures
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2023 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 108, no 17, article id 174413Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Physical Society (APS), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-340288 (URN)10.1103/PhysRevB.108.174413 (DOI)001101171600002 ()2-s2.0-85177045826 (Scopus ID)
Note

QC 20231201

Available from: 2023-12-01 Created: 2023-12-01 Last updated: 2024-02-29Bibliographically approved
Xu, Q., Miranda, I. P., Pereiro, M., Rybakov, F. N., Thonig, D., Sjoeqvist, E., . . . Delin, A. (2023). Metaheuristic conditional neural network for harvesting skyrmionic metastable states. Physical Review Research, 5(4), Article ID 043199.
Open this publication in new window or tab >>Metaheuristic conditional neural network for harvesting skyrmionic metastable states
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2023 (English)In: Physical Review Research, E-ISSN 2643-1564, Vol. 5, no 4, article id 043199Article in journal (Refereed) Published
Abstract [en]

We present a metaheuristic conditional neural-network-based method aimed at identifying physically interest-ing metastable states in a potential energy surface of high rugosity. To demonstrate how this method works, we identify and analyze spin textures with topological charge Q ranging from 1 to -13 (where antiskyrmions have Q < 0) in the Pd/Fe/Ir(111) system, which we model using a classical atomistic spin Hamiltonian based on parameters computed from density functional theory. To facilitate the harvest of relevant spin textures, we make use of the newly developed segment anything model. Spin textures with Q ranging from -3 to -6 are further analyzed using finite-temperature spin-dynamics simulations. We observe that for temperatures up to around 20 K, lifetimes longer than 200 ps are predicted, and that when these textures decay, new topological spin textures are formed. We also find that the relative stability of the spin textures depend linearly on the topological charge, but only when comparing the most stable antiskyrmions for each topological charge. In general, the number of holes (i.e., non-self-intersecting curves that define closed domain walls in the structure) in the spin texture is an important predictor of stability-the more holes, the less stable the texture. Methods for systematic identification and characterization of complex metastable skyrmionic textures-such as the one demonstrated here-are highly relevant for advancements in the field of topological spintronics.

Place, publisher, year, edition, pages
American Physical Society (APS), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-344103 (URN)10.1103/PhysRevResearch.5.043199 (DOI)001128824200002 ()2-s2.0-85179004348 (Scopus ID)
Note

QC 20240301

Available from: 2024-03-01 Created: 2024-03-01 Last updated: 2024-05-07Bibliographically approved
Ryan, S. A., Johnsen, P. C., Elhanoty, M. F., Grafov, A., Li, N., Delin, A., . . . Murnane, M. M. (2023). Optically controlling the competition between spin flips and intersite spin transfer in a Heusler half-metal on sub-100-fs time scales. Science Advances, 9(45), 1428
Open this publication in new window or tab >>Optically controlling the competition between spin flips and intersite spin transfer in a Heusler half-metal on sub-100-fs time scales
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2023 (English)In: Science Advances, E-ISSN 2375-2548, Vol. 9, no 45, p. 1428-Article in journal (Refereed) Published
Abstract [en]

The direct manipulation of spins via light may provide a path toward ultrafast energy-efficient devices. However, distinguishing the microscopic processes that can occur during ultrafast laser excitation in magnetic alloys is challenging. Here, we study the Heusler compound Co2MnGa, a material that exhibits very strong light-induced spin transfers across the entire M-edge. By combining the element specificity of extreme ultraviolet high-harmonic probes with time-dependent density functional theory, we disentangle the competition between three ultrafast light-induced processes that occur in Co2MnGa: same-site Co-Co spin transfer, intersite Co-Mn spin transfer, and ultrafast spin flips mediated by spin-orbit coupling. By measuring the dynamic magnetic asymmetry across the entire M-edges of the two magnetic sublattices involved, we uncover the relative dominance of these processes at different probe energy regions and times during the laser pulse. Our combined approach enables a comprehensive microscopic interpretation of laser-induced magnetization dynamics on time scales shorter than 100 femtoseconds.

Place, publisher, year, edition, pages
American Association for the Advancement of Science (AAAS), 2023
National Category
Condensed Matter Physics Atom and Molecular Physics and Optics
Identifiers
urn:nbn:se:kth:diva-340110 (URN)10.1126/sciadv.adi1428 (DOI)001142520500002 ()37948525 (PubMedID)2-s2.0-85176433605 (Scopus ID)
Note

QC 20231128

Available from: 2023-11-28 Created: 2023-11-28 Last updated: 2024-02-21Bibliographically approved
Chareev, D. A., Khan, M. E., Karmakar, D., Nekrasov, A. N., Nickolsky, M. S., Eriksson, O., . . . Abdel-Hafiez, M. (2023). Stable Sulfuric Vapor Transport and Liquid Sulfur Growth on Transition Metal Dichalcogenides. Crystal Growth & Design, 23(4), 2287-2294
Open this publication in new window or tab >>Stable Sulfuric Vapor Transport and Liquid Sulfur Growth on Transition Metal Dichalcogenides
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2023 (English)In: Crystal Growth & Design, ISSN 1528-7483, E-ISSN 1528-7505, Vol. 23, no 4, p. 2287-2294Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Chemical Society (ACS), 2023
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-330970 (URN)10.1021/acs.cgd.2c01318 (DOI)000955393900001 ()37038405 (PubMedID)2-s2.0-85151269182 (Scopus ID)
Note

Correction in DOI 10.1021/acs.cgd.3c00436

QC 20230705

Available from: 2023-07-05 Created: 2023-07-05 Last updated: 2023-09-05Bibliographically approved
Azimi-Mousolou, V., Bergman, A., Delin, A., Eriksson, O., Pereiro, M., Thonig, D. & Sjöqvist, E. (2023). Transmon probe for quantum characteristics of magnons in antiferromagnets. Physical Review B, 108(9), Article ID 094430.
Open this publication in new window or tab >>Transmon probe for quantum characteristics of magnons in antiferromagnets
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2023 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 108, no 9, article id 094430Article in journal (Refereed) Published
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.

Place, publisher, year, edition, pages
American Physical Society (APS), 2023
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-338392 (URN)10.1103/PhysRevB.108.094430 (DOI)001080546200001 ()2-s2.0-85172422970 (Scopus ID)
Note

QC 20231024

Available from: 2023-10-24 Created: 2023-10-24 Last updated: 2023-10-31Bibliographically approved
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ORCID iD: ORCID iD iconorcid.org/0000-0001-7788-6127

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