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Korenivski, VladislavORCID iD iconorcid.org/0000-0003-2339-1692
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Publikasjoner (10 av 93) Visa alla publikasjoner
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.
Åpne denne publikasjonen i ny fane eller vindu >>Anisotropic and Controllable Gilbert-Bloch Dissipation in Spin Valves
2019 (engelsk)Inngår i: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 122, nr 14, artikkel-id 147201Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
AMER PHYSICAL SOC, 2019
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-251203 (URN)10.1103/PhysRevLett.122.147201 (DOI)000463902800015 ()2-s2.0-85064401197 (Scopus ID)
Merknad

QC 20190724

Tilgjengelig fra: 2019-07-24 Laget: 2019-07-24 Sist oppdatert: 2019-07-24bibliografisk kontrollert
Bondarenko, A., Holmgren, E., Li, Z. W., Ivanov, B. A. & Korenivski, V. (2019). Chaotic dynamics in spin-vortex pairs. Physical Review B, 99, Article ID 054402.
Åpne denne publikasjonen i ny fane eller vindu >>Chaotic dynamics in spin-vortex pairs
Vise andre…
2019 (engelsk)Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 99, artikkel-id 054402Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We report on spin-vortex pair dynamics measured at temperatures low enough to suppress stochastic core motion, thereby uncovering the highly nonlinear intrinsic dynamics of the system. Our analysis shows that the decoupling of the two vortex cores is resonant and can be enhanced by dynamic chaos. We detail the regions of the relevant parameter space, in which the various mechanisms of the resonant core-core dynamics are activated. We show that the presence of chaos can reduce the thermally induced spread in the decoupling time by up to two orders of magnitude.

HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-248013 (URN)10.1103/PhysRevB.99.054402 (DOI)000457728700004 ()2-s2.0-85061380893 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 2014-4546Swedish Research Council, 2018-03526
Merknad

QC 20190402

Tilgjengelig fra: 2019-04-02 Laget: 2019-04-02 Sist oppdatert: 2019-05-20bibliografisk kontrollert
Vilkov, E. A., Mikhailov, G. M., Nikitov, S. A., Safin, A. R., Logunov, M. V., Korenivski, V., . . . Fomin, L. A. (2019). Dynamics of Spatially Inhomogeneous Spin Polarization of Nonequilibrium Conduction Electrons in Magnetic Transitions. Physics of the solid state, 61(6), 941-951
Åpne denne publikasjonen i ny fane eller vindu >>Dynamics of Spatially Inhomogeneous Spin Polarization of Nonequilibrium Conduction Electrons in Magnetic Transitions
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2019 (engelsk)Inngår i: Physics of the solid state, ISSN 1063-7834, E-ISSN 1090-6460, Vol. 61, nr 6, s. 941-951Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

The equation of the dynamics of the magnetic moment motion that has been averaged over the ensemble of nonequilibrium spin-injected electrons in a ferromagnetic transition in the presence of exchange interaction, interaction with an external electromagnetic field, and a thermostat has been obtained taking into account the spatial inhomogeneity of the charge carrier distribution. It has been shown that taking into account the spatial inhomogeneity of the charge carrier distribution in the equation of the dynamics of the magnetic moment motion allows for describing the various processes of electron transfer in the magnetic transition. The probability of quantum transitions of electrons with opposite spin directions, which determine spin relaxation in interaction with a thermostat, has been estimated. It has been shown that the anisotropy of the radiation medium is determined not only by the anisotropy of the sd-exchange tensor, but also by the additional anisotropy that is caused by the electron impulse derivatives of this tensor. The considered phenomena have a great potential for the detection of new effects and development of new devices based on them, including compact tunable radiation sources in the terahertz frequency range, which is obviously difficult to generate.

sted, utgiver, år, opplag, sider
PLEIADES PUBLISHING INC, 2019
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-255212 (URN)10.1134/S1063783419060283 (DOI)000472102000002 ()2-s2.0-85067600782 (Scopus ID)
Merknad

QC 20190903

Tilgjengelig fra: 2019-09-03 Laget: 2019-09-03 Sist oppdatert: 2019-09-03bibliografisk kontrollert
Holmgren, E., Persson, M. & Korenivski, V. (2019). Effects of asymmetry in strongly coupled spin vortex pairs. Journal of Physics D: Applied Physics, 52(10), Article ID 105001.
Åpne denne publikasjonen i ny fane eller vindu >>Effects of asymmetry in strongly coupled spin vortex pairs
2019 (engelsk)Inngår i: Journal of Physics D: Applied Physics, ISSN 0022-3727, E-ISSN 1361-6463, Vol. 52, nr 10, artikkel-id 105001Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Effects of magnetic asymmetry on strongly coupled spin-vortex pairs with parallel core polarization and antiparallel chirality in synthetic nanomagnets are investigated. This includes vortex-core length asymmetry, biasing field asymmetry, and pinning of one of the two vortex cores. Our experimental observations as well as analytical and micromagnetic modeling show how magnetic asymmetry can be used to differentiate magneto-resistively otherwise degenerate multiple stable states of a vortex pair. These results expand the knowledge base for spin vortex arrays in nanostructures and should be useful in light of the recent proposals on coding information into multiple topological spin states, such as single and multiple vortex core/chirality states.

sted, utgiver, år, opplag, sider
IOP PUBLISHING LTD, 2019
Emneord
vortex core pinning, magnetic vortex memory, magnetic vortex pairs
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-241298 (URN)10.1088/1361-6463/aaf8f7 (DOI)000455128200001 ()2-s2.0-85060232971 (Scopus ID)
Merknad

QC 20190222

Tilgjengelig fra: 2019-02-22 Laget: 2019-02-22 Sist oppdatert: 2019-04-29bibliografisk kontrollert
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.
Åpne denne publikasjonen i ny fane eller vindu >>Giant magnetocaloric effect driven by indirect exchange in magnetic multilayers
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2018 (engelsk)Inngår i: PHYSICAL REVIEW MATERIALS, ISSN 2475-9953, Vol. 2, nr 11, artikkel-id 114402Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
AMER PHYSICAL SOC, 2018
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-239779 (URN)10.1103/PhysRevMaterials.2.114402 (DOI)000450572600002 ()2-s2.0-85060615826 (Scopus ID)
Merknad

QC 20190108

Tilgjengelig fra: 2019-01-08 Laget: 2019-01-08 Sist oppdatert: 2019-04-29bibliografisk kontrollert
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.
Åpne denne publikasjonen i ny fane eller vindu >>Magnetic Hysteresis in Nanostructures with Thermally Controlled RKKY Coupling
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2018 (engelsk)Inngår i: Nanoscale Research Letters, ISSN 1931-7573, E-ISSN 1556-276X, Vol. 13, artikkel-id 245Artikkel i tidsskrift (Fagfellevurdert) 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.

sted, utgiver, år, opplag, sider
Springer, 2018
Emneord
Magnetic multilayers, Indirect exchange coupling, Magnetization switching, Magnetic coercivity, Thermo-magnetic effects
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-234599 (URN)10.1186/s11671-018-2669-0 (DOI)000443039100003 ()30136038 (PubMedID)2-s2.0-85052080291 (Scopus ID)
Merknad

QC 20180914

Tilgjengelig fra: 2018-09-14 Laget: 2018-09-14 Sist oppdatert: 2018-09-14bibliografisk kontrollert
Holmgren, E., Bondarenko, A., Ivanov, B. A. & Korenivski, V. (2018). Resonant pinning spectroscopy with spin-vortex pairs. Physical Review B, 97(9), Article ID 094406.
Åpne denne publikasjonen i ny fane eller vindu >>Resonant pinning spectroscopy with spin-vortex pairs
2018 (engelsk)Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 97, nr 9, artikkel-id 094406Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Vortex pairs in magnetic nanopillars with strongly coupled cores and pinning of one of the cores by a morphological defect, are used to perform resonant pinning spectroscopy, in which a microwave excitation applied to the nanopillar produces pinning or depinning of the cores only when the excitation is in resonance with the rotational or gyrational eigenmodes of the specific initial state of the core-core pair. The shift in the eigenmode frequencies between the pinned and depinned states is determined experimentally and explained theoretically, and illustrates the potential for multicore spin-vortex memory with resonant writing of information onto various stable vortex pair states. Further, it is shown how the same resonant spectroscopy techniques applied to a vortex pair can be used as a sensitive nanoscale probe for characterizing morphological defects in magnetic films.

sted, utgiver, år, opplag, sider
American Physical Society, 2018
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-224680 (URN)10.1103/PhysRevB.97.094406 (DOI)000426749400002 ()2-s2.0-85044007173 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 2014-4548
Merknad

QC 20180326

Tilgjengelig fra: 2018-03-26 Laget: 2018-03-26 Sist oppdatert: 2019-04-29bibliografisk kontrollert
Polishchuk, D. M., Polek, T. ,., Kamra, A., Kravets, A., Tovstolytkin, A. ,., Brataas, A. & Korenivski, V. (2018). Spin relaxation in multilayers with synthetic ferrimagnets. Physical Review B, 98(14), Article ID 144401.
Åpne denne publikasjonen i ny fane eller vindu >>Spin relaxation in multilayers with synthetic ferrimagnets
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2018 (engelsk)Inngår i: Physical Review B, ISSN 2469-9950, E-ISSN 2469-9969, Vol. 98, nr 14, artikkel-id 144401Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We demonstrate the strong tunability of the spin-pumping contribution to magnetic damping in a thin-film ferromagnetic free layer interfacing with a synthetic ferrimagnet (SFM), acting as a spin sink, via a thin Cu spacer. The effect strongly depends on the magnetic state of the SFM, a trilayer structure composed of two Fe layers coupled via indirect exchange mediated by a Cr spacer. With increasing Cr thickness, the SFM state undergoes a transition from an antiparallel configuration via a noncollinear configuration to a parallel configuration. We can explain the corresponding nonmonotonous dependence of spin relaxation in the free layer in terms of modulation of the longitudinal spin transport as well as relaxation of the transverse angular momentum in the SFM. The results should be useful for designing high-speed spintronic devices where tunability of spin relaxation is advantageous.

sted, utgiver, år, opplag, sider
American Physical Society, 2018
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-237103 (URN)10.1103/PhysRevB.98.144401 (DOI)000446296400002 ()2-s2.0-85054563141 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 2014-4548Stiftelsen Olle Engkvist Byggmästare
Merknad

QC 20181030

Tilgjengelig fra: 2018-10-30 Laget: 2018-10-30 Sist oppdatert: 2018-10-30bibliografisk kontrollert
Holmgren, E., Bondarenko, A., Persson, M., Ivanov, B. A. & Korenivski, V. (2018). Transient dynamics of strongly coupled spin vortex pairs: Effects of anharmonicity and resonant excitation on inertial switching. Applied Physics Letters, 112(19), Article ID 192405.
Åpne denne publikasjonen i ny fane eller vindu >>Transient dynamics of strongly coupled spin vortex pairs: Effects of anharmonicity and resonant excitation on inertial switching
Vise andre…
2018 (engelsk)Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 112, nr 19, artikkel-id 192405Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

Spin vortices in magnetic nanopillars are used as GHz oscillators, with frequency however essentially fixed in fabrication. We demonstrate a model system of a two-vortex nanopillar, in which the resonance frequency can be changed by an order of magnitude, without using high dc magnetic fields. The effect is due to switching between the two stable states of the vortex pair, and we show that it can be done with low-amplitude fields of sub-ns duration. We detail the relevant vortex-core dynamics and explain how field anharmonicity and phase control can be used to enhance the performance.

sted, utgiver, år, opplag, sider
AMER INST PHYSICS, 2018
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-228429 (URN)10.1063/1.5030855 (DOI)000431980100026 ()
Merknad

QC 20180529

Tilgjengelig fra: 2018-05-29 Laget: 2018-05-29 Sist oppdatert: 2019-04-29bibliografisk kontrollert
Kravets, A., Polishchuk, D., Pashchenko, V. A., Tovstolytkin, A. I. & Korenivski, V. (2017). Current-driven thermo-magnetic switching in magnetic tunnel junctions. Applied Physics Letters, 111(26), Article ID 262401.
Åpne denne publikasjonen i ny fane eller vindu >>Current-driven thermo-magnetic switching in magnetic tunnel junctions
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2017 (engelsk)Inngår i: Applied Physics Letters, ISSN 0003-6951, E-ISSN 1077-3118, Vol. 111, nr 26, artikkel-id 262401Artikkel i tidsskrift (Fagfellevurdert) Published
Abstract [en]

We investigate switching of magnetic tunnel junctions (MTJs) driven by the thermal effect of the transport current through the junctions. The switching occurs in a specially designed composite free layer, which acts as one of the MTJ electrodes, and is due to a current-driven ferro-to-paramagnetic Curie transition with the associated exchange decoupling within the free layer leading to magnetic reversal. We simulate the current and heat propagation through the device and show how heat focusing can be used to improve the power efficiency. The Curie-switch MTJ demonstrated in this work has the advantage of being highly tunable in terms of its operating temperature range, conveniently to or just above room temperature, which can be of technological significance and competitive with the known switching methods using spin-transfer torques.

sted, utgiver, år, opplag, sider
American Institute of Physics (AIP), 2017
HSV kategori
Identifikatorer
urn:nbn:se:kth:diva-221372 (URN)10.1063/1.5009577 (DOI)000418947200019 ()2-s2.0-85040075209 (Scopus ID)
Forskningsfinansiär
Swedish Research Council, 2014-4548
Merknad

QC 20180117

Tilgjengelig fra: 2018-01-17 Laget: 2018-01-17 Sist oppdatert: 2018-01-17bibliografisk kontrollert
Organisasjoner
Identifikatorer
ORCID-id: ORCID iD iconorcid.org/0000-0003-2339-1692