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Publications (7 of 7) Show all publications
Kamra, A., Polishchuk, D., Korenivski, V. & Brataas, A. (2019). Anisotropic and Controllable Gilbert-Bloch Dissipation in Spin Valves. Physical Review Letters, 122(14), Article ID 147201.
Open this publication in new window or tab >>Anisotropic and Controllable Gilbert-Bloch Dissipation in Spin Valves
2019 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 122, no 14, article id 147201Article in journal (Refereed) Published
Abstract [en]

Spin valves form a key building block in a wide range of spintronic concepts and devices from magnetoresistive read heads to spin-transfer-torque oscillators. We elucidate the dependence of the magnetic damping in the free layer on the angle its equilibrium magnetization makes with that in the fixed layer. The spin pumping-mediated damping is anisotropic and tensorial, with Gilbert- and Bloch-like terms. Our investigation reveals a mechanism for tuning the free layer damping in situ from negligible to a large value via the orientation of fixed layer magnetization, especially when the magnets are electrically insulating. Furthermore, we expect the Bloch contribution that emerges from the longitudinal spin accumulation in the nonmagnetic spacer to play an important role in a wide range of other phenomena in spin valves.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2019
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-251203 (URN)10.1103/PhysRevLett.122.147201 (DOI)000463902800015 ()2-s2.0-85064401197 (Scopus ID)
Note

QC 20190724

Available from: 2019-07-24 Created: 2019-07-24 Last updated: 2019-07-24Bibliographically approved
Polishchuk, D., Tykhonenko-Polishchuk, Y., Holmgren, E., Kravets, A., Tovstolytkin, A. I. & Korenivski, V. (2018). Giant magnetocaloric effect driven by indirect exchange in magnetic multilayers. PHYSICAL REVIEW MATERIALS, 2(11), Article ID 114402.
Open this publication in new window or tab >>Giant magnetocaloric effect driven by indirect exchange in magnetic multilayers
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2018 (English)In: PHYSICAL REVIEW MATERIALS, ISSN 2475-9953, Vol. 2, no 11, article id 114402Article in journal (Refereed) Published
Abstract [en]

Indirect exchange coupling in magnetic multilayers, also known as the Ruderman-Kittel-Kasuya-Yosida (RKKY) interaction, is highly effective in controlling the interlayer alignment of the magnetization. This coupling is typically fixed at the stage of the multilayer fabrication and does not allow ex situ control needed for device applications. In addition to the orientational control, it is highly desirable to also control the magnitude of the intralayer magnetization, ideally, being able to switch it on/off by switching the relevant RKKY coupling. Here we demonstrate a magnetic multilayer material incorporating thermally and field-controlled RKKY exchange, focused on a dilute ferromagnetic alloy layer and driving it though its Curie transition. Such on/off magnetization switching of a thin ferromagnet, performed repeatedly and fully reproducibly within a low-field sweep, results in a giant magnetocaloric effect, with an estimated isothermal entropy change of Delta S approximate to -10 mJ cm(-3) K(-1 )under an external field of similar to 10 mT, which greatly exceeds the performance of the best rare-earth based materials used in the adiabatic-demagnetization refrigeration systems.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2018
National Category
Nano Technology
Identifiers
urn:nbn:se:kth:diva-239779 (URN)10.1103/PhysRevMaterials.2.114402 (DOI)000450572600002 ()2-s2.0-85060615826 (Scopus ID)
Note

QC 20190108

Available from: 2019-01-08 Created: 2019-01-08 Last updated: 2019-04-29Bibliographically approved
Polishchuk, D., Tykhonenko-Polishchuk, Y., Borynskyi, V., Kravets, A., Tovstolytkin, A. & Korenivski, V. (2018). Magnetic Hysteresis in Nanostructures with Thermally Controlled RKKY Coupling. Nanoscale Research Letters, 13, Article ID 245.
Open this publication in new window or tab >>Magnetic Hysteresis in Nanostructures with Thermally Controlled RKKY Coupling
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2018 (English)In: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 13, article id 245Article in journal (Refereed) Published
Abstract [en]

Mechanisms of the recently demonstrated ex-situ thermal control of the indirect exchange coupling in magnetic multilayer are discussed for different designs of the spacer layer. Temperature-induced changes in the hysteresis of magnetization are shown to be associated with different types of competing interlayer exchange interactions. Theoretical analysis indicates that the measured step-like shape and hysteresis of the magnetization loops is due to local in-plane magnetic anisotropy of nano-crystallites within the strongly ferromagnetic films. Comparison of the experiment and theory is used to contrast the mechanisms of the magnetization switching based on the competition of (i) indirect (RKKY) and direct (non-RKKY) interlayer exchange interactions as well as (ii) indirect ferromagnetic and indirect antiferromagnetic (both of RKKY type) interlayer exchange. These results, detailing the rich magnetic phase space of the system, should help enable the practical use of RKKY for thermally switching the magnetization in magnetic multilayers.

Place, publisher, year, edition, pages
Springer, 2018
Keywords
Magnetic multilayers, Indirect exchange coupling, Magnetization switching, Magnetic coercivity, Thermo-magnetic effects
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-234599 (URN)10.1186/s11671-018-2669-0 (DOI)000443039100003 ()30136038 (PubMedID)2-s2.0-85052080291 (Scopus ID)
Note

QC 20180914

Available from: 2018-09-14 Created: 2018-09-14 Last updated: 2018-09-14Bibliographically approved
Kravets, A., Gomonay, O. V., Polishchuk, D., Tykhonenko-Polishchuk, Y. .., Polek, T. I., Tovstolytkin, A. I. & Korenivski, V. (2017). Effect of nanostructure layout on spin pumping phenomena in antiferromagnet/nonmagnetic metal/ferromagnet multilayered stacks. AIP Advances, 7(5), Article ID 056312.
Open this publication in new window or tab >>Effect of nanostructure layout on spin pumping phenomena in antiferromagnet/nonmagnetic metal/ferromagnet multilayered stacks
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2017 (English)In: AIP Advances, ISSN 2158-3226, E-ISSN 2158-3226, Vol. 7, no 5, article id 056312Article in journal (Refereed) Published
Abstract [en]

In this work we focus on magnetic relaxation in Mn80Ir20(12 nm)/Cu(6 nm)/Py(dF) antiferromagnet/Cu/ferromagnet (AFM/Cu/FM) multilayers with different thickness of the ferromagnetic permalloy layer. An effective FM-AFM interaction mediated via the conduction electrons in the nonmagnetic Cu spacer - the spin-pumping effect - is detected as an increase in the linewidth of the ferromagnetic resonance (FMR) spectra and a shift of the resonant magnetic field. We further find experimentally that the spin-pumping-induced contribution to the linewidth is inversely proportional to the thickness of the Py layer. We show that this thickness dependence likely originates from the dissipative dynamics of the free and localized spins in the AFM layer. The results obtained could be used for tailoring the dissipative properties of spintronic devices incorporating antiferromagnetic layers.

Place, publisher, year, edition, pages
American Institute of Physics Inc., 2017
Keywords
Antiferromagnetic materials, Ferromagnetic materials, Ferromagnetic resonance, Ferromagnetism, Iridium, Magnetic multilayers, Manganese, Nickel alloys, Antiferromagnetic layers, Conduction electrons, Different thickness, Dissipative dynamics, Dissipative properties, Ferromagnetic resonance (FMR), Spin-pumping effects, Thickness dependence, Pumps
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-207349 (URN)10.1063/1.4975694 (DOI)000402797100251 ()2-s2.0-85011661357 (Scopus ID)
Note

QC 20170522

Available from: 2017-05-22 Created: 2017-05-22 Last updated: 2017-11-29Bibliographically approved
Polishchuk, D., Tykhonenko-Polishchuk, Y. .., Kravets, A. & Korenivski, V. (2017). Thermal switching of indirect interlayer exchange in magnetic multilayers. Europhysics letters, 118(3), Article ID 37006.
Open this publication in new window or tab >>Thermal switching of indirect interlayer exchange in magnetic multilayers
2017 (English)In: Europhysics letters, ISSN 0295-5075, E-ISSN 1286-4854, Vol. 118, no 3, article id 37006Article in journal (Refereed) Published
Abstract [en]

We propose a magnetic multilayer layout, in which the indirect exchange coupling (IEC also known as RKKY) can be switched on and off by a slight change in temperature. We demonstrate such on/off IEC switching in a Fe/Cr/FeCr-based system and obtain thermal switching widths as small as 10-20 K, essentially in any desired temperature range, including at or just above room temperature. These results add a new dimension of tunable thermal control to IEC in magnetic nanostructures, highly technological in terms of available materials and operating physical regimes.

Place, publisher, year, edition, pages
Institute of Physics Publishing, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-216502 (URN)10.1209/0295-5075/118/37006 (DOI)000407226300021 ()2-s2.0-85024113273 (Scopus ID)
Note

QC 20171201

Available from: 2017-12-01 Created: 2017-12-01 Last updated: 2017-12-01Bibliographically approved
Polishchuk, D., Tykhonenko-Polishchuk, Y. O. O., Holmgren, E., Kravets, A. & Korenivski, V. (2017). Thermally induced antiferromagnetic exchange in magnetic multilayers. Physical Review B, 96(10), Article ID 104427.
Open this publication in new window or tab >>Thermally induced antiferromagnetic exchange in magnetic multilayers
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2017 (English)In: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 96, no 10, article id 104427Article in journal (Refereed) Published
Abstract [en]

We demonstrate sharp thermally induced switching between ferromagnetic and antiferromagnetic RKKY ( Ruderman-Kittel-Kasuya-Yosida) exchange in a spin-valve with the spacer incorporating a thin diluted ferromagnetic layer as the core. We illustrate the mechanism behind the effect as being due to a change in the effective thickness of the spacer induced by the Curie transition into its paramagnetic state. The ability to switch between ferromagnetic and antiferromagnetic states in a magnetic multilayer by a slight change in temperature may lead to new types of spin-thermoelectronic devices for use in such applications as memory or oscillators.

Place, publisher, year, edition, pages
AMER PHYSICAL SOC, 2017
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-215448 (URN)10.1103/PhysRevB.96.104427 (DOI)000411320900002 ()2-s2.0-85029945218 (Scopus ID)
Note

QC 20171019

Available from: 2017-10-19 Created: 2017-10-19 Last updated: 2019-04-29Bibliographically approved
Polishchuk, D., Tykhonenko-Polishchuk, Y. O. O., Kravets, A., Tovstolytkin, A. I., Dzhezherya, Y. I. I., Pogorily, A. M. & Korenivski, V. (2016). Ferromagnetic resonance in nanostructures with temperature-controlled interlayer interaction. Low temperature physics (Woodbury, N.Y., Print), 42(9), 761-767
Open this publication in new window or tab >>Ferromagnetic resonance in nanostructures with temperature-controlled interlayer interaction
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2016 (English)In: Low temperature physics (Woodbury, N.Y., Print), ISSN 1063-777X, E-ISSN 1090-6517, Vol. 42, no 9, p. 761-767Article in journal (Refereed) Published
Abstract [en]

This study is a comprehensive analysis of a multilayer F-1/f(d)/F-2pin structure's magnetic resonance properties, wherein F-1 and F-2pin are the free and exchange-coupled strong magnetic layers, and f is the weakly magnetic layer with a Curie point in the room temperature region. Depending on the magnetic state of the spacer f (ferromagnetic or paramagnetic) the exchange interaction between the F-2 and F-2pin layers becomes a function of the temperature, which opens up opportunities for practical applications. The obtained results show that the interlayer exchange coupling can be enhanced by decreasing the thickness of the spacer d, or by lowering the temperature. Strengthening the exchange coupling leads to a stronger manifestation of unidirectional anisotropy in the ferromagnetic resonance layer F-1, as well as to a broadening of the resonance line that is atypical for thin films. The observed features are analyzed in the context of comparing the effects of two different natures: the influence of the spacer d and the influence of the temperature. Thus, the behavior of changes to the unidirectional anisotropy remains the same given variation of both the thickness of the spacer and the temperature. However the broadening of the magnetic resonance line is more sensitive to changes in the interlayer interaction caused by variation of d, and is less susceptible to changes caused by temperature.

Place, publisher, year, edition, pages
American Institute of Physics (AIP), 2016
National Category
Condensed Matter Physics
Identifiers
urn:nbn:se:kth:diva-196439 (URN)10.1063/1.4964116 (DOI)000385872700008 ()2-s2.0-84990996539 (Scopus ID)
Funder
Stiftelsen Olle Engkvist ByggmästareSwedish Research Council, VR 2014-4548
Note

QC 20161129

Available from: 2016-11-29 Created: 2016-11-14 Last updated: 2017-11-29Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0001-5028-8928

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