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Pogoryelov, Y., Pereiro, M., Jana, S., Kumar, A., Akansel, S., Ranjbar, M., . . . Arena, D. A. (2020). Nonreciprocal spin pumping damping in asymmetric magnetic trilayers. Physical Review B, 101(5), Article ID 054401.
Open this publication in new window or tab >>Nonreciprocal spin pumping damping in asymmetric magnetic trilayers
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2020 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 101, no 5, article id 054401Article in journal (Refereed) Published
Abstract [en]

In magnetic trilayer systems, spin pumping is generally addressed as a reciprocal mechanism characterized by one unique spin-mixing conductance common to both interfaces. However, this assumption is questionable in cases where different types of interfaces are present. Here, we present a general theory for analyzing spin pumping in cases with more than one unique interface and where the magnetic coupling is allowed to be noncollinear. The theory is applied to analyze layer-resolved ferromagnetic resonance experiments on the trilayer system Ni80Fe20/Ru/Fe49Co49V2 where the Ru spacer thickness is varied to tune the indirect exchange coupling. It is demonstrated that the equation of motion of macrospins driven by spin pumping need to be modified in case of noncollinear coupling. Our analysis also shows that the spin pumping in trilayer systems with dissimilar magnetic layers, in general, is nonreciprocal.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2020
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-267737 (URN)10.1103/PhysRevB.101.054401 (DOI)000510745200002 ()
Note

QC 20200219

Available from: 2020-02-19 Created: 2020-02-19 Last updated: 2020-02-19Bibliographically approved
Haidar, M., Awad, A. A., Dvornik, M., Khymyn, R., Houshang, A. & Åkerman, J. (2019). A single layer spin-orbit torque nano-oscillator. Nature Communications, 10, Article ID 2362.
Open this publication in new window or tab >>A single layer spin-orbit torque nano-oscillator
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2019 (English)In: Nature Communications, ISSN 2041-1723, E-ISSN 2041-1723, Vol. 10, article id 2362Article in journal (Refereed) Published
Abstract [en]

Spin torque and spin Hall effect nano-oscillators generate high intensity spin wave auto-oscillations on the nanoscale enabling novel microwave applications in spintronics, magnonics, and neuromorphic computing. For their operation, these devices require externally generated spin currents either from an additional ferromagnetic layer or a material with a high spin Hall angle. Here we demonstrate highly coherent field and current tunable microwave signals from nano-constrictions in single 15-20 nm thick permalloy layers with oxide interfaces. Using a combination of spin torque ferromagnetic resonance measurements, scanning micro-Brillouin light scattering microscopy, and micromagnetic simulations, we identify the auto-oscillations as emanating from a localized edge mode of the nano-constriction driven by spin-orbit torques. Our results pave the way for greatly simplified designs of auto-oscillating nano-magnetic systems only requiring single ferromagnetic layers with oxide interfaces.

Place, publisher, year, edition, pages
Nature Publishing Group, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-252967 (URN)10.1038/s41467-019-10120-4 (DOI)000469320900004 ()31142758 (PubMedID)2-s2.0-85067048844 (Scopus ID)
Note

QC 20190812

Available from: 2019-08-12 Created: 2019-08-12 Last updated: 2019-08-12Bibliographically approved
Albertsson, D. I., Zahedinejad, M., Åkerman, J., Rodriguez, S. & Rusu, A. (2019). Compact Macrospin-Based Model of Three-Terminal Spin-Hall Nano Oscillators. IEEE transactions on magnetics, 55(10), Article ID 4003808.
Open this publication in new window or tab >>Compact Macrospin-Based Model of Three-Terminal Spin-Hall Nano Oscillators
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2019 (English)In: IEEE transactions on magnetics, ISSN 0018-9464, E-ISSN 1941-0069, Vol. 55, no 10, article id 4003808Article in journal (Refereed) Published
Abstract [en]

Emerging spin-torque nano oscillators (STNOs) and spin-Hall nano oscillators (SHNOs) are potential candidates for microwave applications. Recent advances in three-terminal magnetic tunnel junction (MTJ)-based SHNOs opened the possibility to develop more reliable and well-controlled oscillators, thanks to individual spin Hall-driven precession excitation and read-out paths. To develop hybrid systems by integrating three-terminal SHNOs and CMOS circuits, an electrical model able to capture the analog characteristics of three-terminal SHNOs is needed. This model needs to be compatible with current electric design automation (EDA) tools. This work presents a comprehensive macrospin-based model of three-terminal SHNOs able to describe the dc operating point, frequency modulation, phase noise, and output power. Moreover, the effect of voltage-controlled magnetic anisotropy (VCMA) is included. The model shows good agreement with experimental measurements and could be used in developing hybrid three-terminal SHNO/CMOS systems.

Place, publisher, year, edition, pages
IEEE Press, 2019
Keywords
Compact model, magnetic tunnel junction (MTJ), spin-Hall nano oscillator (SHNO)
National Category
Other Electrical Engineering, Electronic Engineering, Information Engineering
Research subject
Electrical Engineering
Identifiers
urn:nbn:se:kth:diva-259715 (URN)10.1109/TMAG.2019.2925781 (DOI)000487191400001 ()2-s2.0-85077499904 (Scopus ID)
Funder
Swedish Research Council
Note

QC 20190930

Available from: 2019-09-20 Created: 2019-09-20 Last updated: 2020-02-04Bibliographically approved
Nguyen, T. N., Fedotova, J., Kasiuk, J., Wu, W.-B. -., Przewoznik, J., Kapusta, C., . . . Åkerman, J. (2019). Enhanced Perpendicular Exchange Bias in Co/Pd Antidot Arrays. Paper presented at 5th International Conference of Asian-Union-of-Magnetics-Societies (IcAUMS), JUN 03-07, 2018, SOUTH KOREA. Journal of Electronic Materials, 48(3), 1492-1497
Open this publication in new window or tab >>Enhanced Perpendicular Exchange Bias in Co/Pd Antidot Arrays
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2019 (English)In: Journal of Electronic Materials, ISSN 0361-5235, E-ISSN 1543-186X, Vol. 48, no 3, p. 1492-1497Article in journal (Refereed) Published
Abstract [en]

Magnetic nanostructures revealing the exchange bias (EB) effect have attracted much interest in recent years due to their promising applications in spintronics, magneticsensing and recording devices with various functionalities. In this paper, we report on the perpendicular exchange bias effect in a multilayered thin film composed of [Co/Pd] ferromagnetic multilayers exchange-coupled to an antiferromagnetic IrMn. The film was deposited on a porous anodized titania template. Influences of the films' surface morphology as well as the order of layers deposited on the EB effect were studied. The enhancements of the EB field H-EB (up to 30%) and the coercive field H-C (two times) were achieved in the nanoporous films relative to their continuous film counterparts, which could be attributed to the specific morphology of the porous surfaces.

Place, publisher, year, edition, pages
SPRINGER, 2019
Keywords
Multilayered Co/Pd thin films, porous TiO2 templates, perpendicular magnetic anisotropy, exchange bias
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-244494 (URN)10.1007/s11664-018-06847-3 (DOI)000457748600028 ()2-s2.0-85058164693 (Scopus ID)
Conference
5th International Conference of Asian-Union-of-Magnetics-Societies (IcAUMS), JUN 03-07, 2018, SOUTH KOREA
Note

QC 20190328

Available from: 2019-03-28 Created: 2019-03-28 Last updated: 2019-03-29Bibliographically approved
Jiang, S., Ahlberg, M., Chung, S., Houshang, A., Ferreira, R., Freitas, P. P. & Åkerman, J. (2019). Magnetodynamics in orthogonal nanocontact spin-torque nano-oscillators based on magnetic tunnel junctions. Applied Physics Letters, 115(15), Article ID 152402.
Open this publication in new window or tab >>Magnetodynamics in orthogonal nanocontact spin-torque nano-oscillators based on magnetic tunnel junctions
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2019 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 115, no 15, article id 152402Article in journal (Refereed) Published
Abstract [en]

We demonstrate field and current controlled magnetodynamics in nanocontact spin-torque nano-oscillators based on orthogonal magnetic tunnel junctions. We systematically analyze the microwave properties (frequency f, linewidth Delta f, power P, and frequency tunability df/dI) with their physical origins-perpendicular magnetic anisotropy, dampinglike and fieldlike spin transfer torque (STT), and voltage-controlled magnetic anisotropy (VCMA). These devices present several advantageous characteristics: high emission frequencies (f>20 GHz), high frequency tunability (df/dI=0.25 GHz/mA), and zero-field operation (f similar to 4 GHz). Furthermore, detailed investigation of f(H, I) reveals that df/dI is mostly governed by the large VCMA [287 fJ/(V m)], while STT plays a negligible role.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2019
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-263675 (URN)10.1063/1.5121356 (DOI)000492035500038 ()2-s2.0-85073259843 (Scopus ID)
Note

QC 20191108

Available from: 2019-11-08 Created: 2019-11-08 Last updated: 2019-11-08Bibliographically approved
Fulara, H., Zahedinejad, M., Khymyn, R., Awad, A. A., Muralidhar, S., Dvornik, M. & Åkerman, J. (2019). Spin-orbit torque-driven propagating spin waves. Science Advances, 5(9), Article ID eaax8467.
Open this publication in new window or tab >>Spin-orbit torque-driven propagating spin waves
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2019 (English)In: Science Advances, E-ISSN 2375-2548, Vol. 5, no 9, article id eaax8467Article in journal (Refereed) Published
Abstract [en]

Spin-orbit torque (SOT) can drive sustained spin wave (SW) auto-oscillations in a class of emerging microwave devices known as spin Hall nano-oscillators (SHNOs), which have highly nonlinear properties governing robust mutual synchronization at frequencies directly amenable to high-speed neuromorphic computing. However, all demonstrations have relied on localized SW modes interacting through dipolar coupling and/or direct exchange. As nanomagnonics requires propagating SWs for data transfer and additional computational functionality can be achieved using SW interference, SOT-driven propagating SWs would be highly advantageous. Here, we demonstrate how perpendicular magnetic anisotropy can raise the frequency of SOT-driven auto-oscillations in magnetic nanoconstrictions well above the SW gap, resulting in the efficient generation of field and current tunable propagating SWs. Our demonstration greatly extends the functionality and design freedom of SHNOs, enabling long-range SOT-driven SW propagation for nanomagnonics, SW logic, and neuromorphic computing, directly compatible with CMOS technology.

Place, publisher, year, edition, pages
American Association for the Advancement of Science, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-263372 (URN)10.1126/sciadv.aax8467 (DOI)000491128800073 ()2-s2.0-85072761314 (Scopus ID)
Note

QC 20191118

Available from: 2019-11-18 Created: 2019-11-18 Last updated: 2019-11-20Bibliographically approved
Burgos-Parra, E., Keatley, P. S., Redjai Sani, S., Durrenfeld, P., Åkerman, J. & Hicken, R. J. (2019). Time-resolved imaging of magnetization dynamics in double nanocontact spin torque vortex oscillator devices. Physical Review B, 100(13), Article ID 134439.
Open this publication in new window or tab >>Time-resolved imaging of magnetization dynamics in double nanocontact spin torque vortex oscillator devices
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2019 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 100, no 13, article id 134439Article in journal (Refereed) Published
Abstract [en]

Double nanocontact (NC) spin transfer vortex oscillator devices, in which NCs of 100-nm diameter have center-to-center separation ranging from 200 to 1100 nm, have been studied by means of electrical measurements and time-resolved scanning Kerr microscopy (TRSKM). The NCs were positioned close to the edge of the top electrical contact so that the magnetization dynamics of the adjacent region could be probed optically. The electrical measurements showed different ranges of frequency operation for devices with different NC separations. For 900-nm NC separation, TRSKM showed magnetic contrast consistent with the formation of a magnetic vortex at each NC, while for 200-nm NC separation a lack of magnetic contrast near the NC region suggests that the magnetization dynamics occur closer to the NC and underneath the top contact. TRSKM also reveals the presence of additional localized dynamical features far from the NCs, which are not seen by electrical measurements; has not been reported previously for double NCs with different separations; and provides insight into how the dynamic state of the phase-locked oscillators is established and stabilized.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-264157 (URN)10.1103/PhysRevB.100.134439 (DOI)000493513500002 ()2-s2.0-85074947136 (Scopus ID)
Note

QC 20191210

Available from: 2019-12-10 Created: 2019-12-10 Last updated: 2019-12-19Bibliographically approved
Fazlali, M., Banuazizi, S. A., Ahlberg, M., Dvornik, M., Sani, S. R., Mohseni, S. M. & Åkerman, J. (2019). Tuning exchange-dominated spin-waves using lateral current spread in nanocontact spin-torque nano-oscillators. Journal of Magnetism and Magnetic Materials, 492, Article ID UNSP 165503.
Open this publication in new window or tab >>Tuning exchange-dominated spin-waves using lateral current spread in nanocontact spin-torque nano-oscillators
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2019 (English)In: Journal of Magnetism and Magnetic Materials, ISSN 0304-8853, E-ISSN 1873-4766, Vol. 492, article id UNSP 165503Article in journal (Refereed) Published
Abstract [en]

We present an efficient method to tailor propagating spin waves in quasi-confined systems. We use nanocontact spin-torque nano-oscillators based on NiFe/Cu/Co spin-valves and study the ferromagnetic and spin-wave resonances (FMR and SWR) of both layers. We employ homodyne-detected ferromagnetic resonance spectroscopy, resembling spin-torque FMR, to detect the magnetodynamics. The external field is applied in-plane, giving a parallel configuration of the magnetic layers, which do not provide any spin-transfer torque. Instead, the excitation is caused by the Oersted field. By varying the thickness of the bottom Cu electrode (t(Cu)) of the devices, we tune the current distribution in the samples, and thereby the Oersted field, which governs the spin wave characteristics. Both the average k-vector and the bandwidth of the SWR increases as t(Cu) increases.

Place, publisher, year, edition, pages
ELSEVIER, 2019
Keywords
Spin-wave, Spin torque nano-oscillator, Ferromagnetic resonance
National Category
Other Physics Topics
Identifiers
urn:nbn:se:kth:diva-260152 (URN)10.1016/j.jmmm.2019.165503 (DOI)000483912600045 ()2-s2.0-85073641457 (Scopus ID)
Note

QC 20191001

Available from: 2019-10-01 Created: 2019-10-01 Last updated: 2020-02-04Bibliographically approved
Mazraati, H., Etesami, S. R., Banuazizi, S. A., Chung, S., Houshang, A., Awad, A. A., . . . Åkerman, J. (2018). Auto-oscillating Spin-Wave Modes of Constriction-Based Spin Hall Nano-oscillators in Weak In-Plane Fields. Physical Review Applied, 10(5), Article ID 054017.
Open this publication in new window or tab >>Auto-oscillating Spin-Wave Modes of Constriction-Based Spin Hall Nano-oscillators in Weak In-Plane Fields
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2018 (English)In: Physical Review Applied, E-ISSN 2331-7019, Vol. 10, no 5, article id 054017Article in journal (Refereed) Published
Abstract [en]

We experimentally study the auto-oscillating spin-wave modes in Ni(80)Fc(20)/beta-W constriction-based spin Hall nano-oscillators as a function of bias current, strength of the in-plane applied field, and azimuthal field angle in the low-field range of 40-80 mT. We observe two different spin-wave modes: (i) a linearlike mode confined to the internal field minima near the edges of the nanoconstriction, and only weakly dependent on the bias current and the applied-field angle, and (ii) a second, lower-frequency mode with significantly higher threshold current and stronger dependence on both the bias current and the externalfield angle. Micromagnetic modeling qualitatively reproduces the experimental data and reveals that the second mode is a spin-wave bullet and that the spin Hall nano-oscillator mode hops between the two modes, resulting in a substantial increase in linewidths. In contrast to the linearlike mode, the bullet is localized in the middle of the constriction and shrinks with increasing bias current. Using intrinsic frequency doubling at zero field angle, we can reach frequencies above 9 GHz in fields as low as 40 mT, which is important for the development of low-field spintronic oscillators with applications in microwave-signal generation and neuromorphic computing.

Place, publisher, year, edition, pages
American Physical Society, 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-239478 (URN)10.1103/PhysRevApplied.10.054017 (DOI)000449412100003 ()2-s2.0-85056389030 (Scopus ID)
Funder
EU, Horizon 2020, 687676
Note

QC 20181126

Available from: 2018-11-26 Created: 2018-11-26 Last updated: 2018-11-26Bibliographically approved
Zahedinejad, M., Mazraati, H., Fulara, H., Yue, J., Jiang, S., Awad, A. A. & Åkerman, J. (2018). CMOS compatible W/CoFeB/MgO spin Hall nano-oscillators with wide frequency tunability. Applied Physics Letters, 112(13), Article ID 132404.
Open this publication in new window or tab >>CMOS compatible W/CoFeB/MgO spin Hall nano-oscillators with wide frequency tunability
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2018 (English)In: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, no 13, article id 132404Article in journal (Refereed) Published
Abstract [en]

We demonstrate low-operational-current W/Co20Fe60B20/MgO spin Hall nano-oscillators (SHNOs) on highly resistive silicon (HiR-Si) substrates. Thanks to a record high spin Hall angle of the beta-phase W (theta(SH) = -0.53), a very low threshold current density of 3.3 x 10(7) A/cm(2) can be achieved. Together with their very wide frequency tunability (7-28GHz), promoted by a moderate perpendicular magnetic anisotropy, HiR-Si/W/CoFeB based SHNOs are potential candidates for wide-band microwave signal generation. Their CMOS compatibility offers a promising route towards the integration of spintronic microwave devices with other on-chip semiconductor microwave components.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2018
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-226793 (URN)10.1063/1.5022049 (DOI)000429072800015 ()2-s2.0-85044750620 (Scopus ID)
Funder
Swedish Foundation for Strategic Research Swedish Research CouncilKnut and Alice Wallenberg FoundationEU, FP7, Seventh Framework Programme, 307144
Note

QC 20180504

Available from: 2018-05-04 Created: 2018-05-04 Last updated: 2018-09-07Bibliographically approved
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-3513-6608

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