| 1. |
- Borynskyi, Vladyslav, et al.
(författare)
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Spin-wave Resonance in Arrays of Nanoscale Synthetic-antiferromagnets
- 2022
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Ingår i: Proceedings of the 2022 IEEE 12th International Conference "Nanomaterials: Applications and Properties", NAP 2022. - : Institute of Electrical and Electronics Engineers (IEEE).
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Konferensbidrag (refereegranskat)abstract
- The study concerns dynamics of standing spin waves in arrays of sub-100 nm elliptic synthetic-antiferromagnet (SAF) nanodisks. We performed a detailed ferromagnetic resonance analysis in conjunction with micro magnetic modeling to find out several prominent traits of such systems. One broad line is shown to be the sole resonant response for a SAF of the considered sizes. We demonstrate that this mode is degenerated, and its excitation map resembles a superposition of in-center and edge-type oscillations. We also show how this hybrid excitation leads to almost twofold enhancement in the shape-induced anisotropy of the mode.
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| 2. |
- Borynskyi, V. Yu, et al.
(författare)
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Higher-order ferromagnetic resonances in periodic arrays of synthetic-antiferromagnet nanodisks
- 2021
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 119:19
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Tidskriftsartikel (refereegranskat)abstract
- We investigate spin dynamics in nanodisk arrays of synthetic-antiferromagnets (SAF) made of Py/NiCu/Py trilayers, where the NiCu spacer undergoes a Curie transition at about 200 K. The observed ferromagnetic resonance spectra have three distinct resonance modes at room temperature, which are fully recreated in our micromagnetic simulations, showing also how the intra-SAF asymmetry can be used to create and control the higher-order resonances in the structure. Below the Curie temperature of the spacer, the system effectively transitions into a single-layer nanodisk array with only two resonance modes. Our results show how multilayering of nanoarrays can add tunable GHz functionality relevant for such rapidly developing fields as magnetic metamaterials, magnonic crystals, arrays of spin-torque oscillators, and neuromorphic junctions.
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| 3. |
- Borynskyi, V. Yu, et al.
(författare)
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Thermomagnetic transition in nanoscale synthetic antiferromagnets Py/NiCu/Py
- 2023
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 49:7, s. 863-869
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Tidskriftsartikel (refereegranskat)abstract
- Using the method of SQUID magnetometry, the features of the antiferromagnet-ferromagnet thermomagnetic transition in arrays of the nanosized disks of Py/NiCu/Py synthetic antiferromagnets (SAFs) have been investigated. The effective interlayer interaction in individual SAFs “ferromagnet/diluted ferromagnet/ferromagnet” (F2/f/F1) changes from high-temperature antiferromagnetic to low-temperature ferromagnetic upon the transition at the Curie temperature T C f of the interlayer f. Temperature dependence of the magnetic parameters of individual layers and their effect on the features of the thermomagnetic transition are determined. The observed properties are important for the development of temperature-controlled nanoscale SAFs and multilayer nanostructures based on them.
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| 4. |
- Demchenko, Lesya, et al.
(författare)
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Structural and Magnetic Transitions in Aged Shape Memory Cu-Al-Mn and Cu-Al-Mn-Fe Alloys
- 2023
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Ingår i: Proceedings of the 2023 IEEE 13th International Conference Nanomaterials: Applications and Properties, NAP 2023. - : Institute of Electrical and Electronics Engineers (IEEE). ; , s. NMM041-NMM044
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Konferensbidrag (refereegranskat)abstract
- A comparative analysis of the structural and magnetic behavior of Cu-Al-Mn and Cu-Al-Mn-Fe alloys depending on their heat treatment is carried out. The influence of low-temperature aging on the behavior of temperature induced martensitic transformation was established. The difference in magnetic behavior of alloys is a consequence of the formation of the ferromagnetic (Cu,Mn)3Al and (Fe,Mn)3Al Heusler phases during isothermal aging and the transition to a superparamagnetic state. In alloys doped with iron, antiferromagnetic ordering can prevail over ferromagnetic. The precipitates create a significant cumulative effect on the character and characteristic temperature of thermoelastic martensite transformation (MT), as well as on mechanical and magnetic behavior.
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| 5. |
- Dzhezherya, Yu., et al.
(författare)
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Ultrafast Inertia-Free Switching of Double Magnetic Tunnel Junctions
- 2024
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Ingår i: IEEE Transactions on Magnetics. - : Institute of Electrical and Electronics Engineers (IEEE). - 0018-9464 .- 1941-0069. ; 60:5
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the switching of a magnetic nanoparticle comprising the middle free layer of a memory cell based on a double magnetic tunnel junction under the combined effect of spin-polarized current and weak on-chip magnetic field. We obtain the timing and amplitude parameters for the current and field pulses needed to achieve 100 ps range inertia-free switching under least-power dissipation. The considered method does not rely on the stochastics of thermal agitation of the magnetic nanoparticle typically accompanying spin-torque switching. The regime of ultimate switching speed efficiency found in this work is promising for applications in high-performance nonvolatile memory.
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| 6. |
- Iurchuk, Vadym, et al.
(författare)
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All-Electrical Operation of a Curie Switch at Room Temperature
- 2023
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Ingår i: Physical Review Applied. - : American Physical Society (APS). - 2331-7019. ; 20:2
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Tidskriftsartikel (refereegranskat)abstract
- We present all-electrical operation of a FexCr1-x-based Curie switch at room temperature. More specifically, we study the current-induced thermally driven transition from ferromagnetic to antiferromagnetic Magnetometry measurements at different temperatures show that the transition from the ferromagnetic to the antiferromagnetic coupling at zero field is observed at approximately 325 K. Analytical modeling confirms that the observed temperature-dependent transition from indirect ferromagnetic to indirect antiferromagnetic interlayer exchange coupling originates from the modification of the effective interlayer exchange constant through the ferromagnetic-to-paramagnetic transition in the Fe17.5Cr82.5 spacer with minor contributions from the thermally driven variations of the magnetization and magnetic anisotropy of the Fe layers. Room-temperature current-in-plane magnetotransport measurements on the patterned Fe/Cr/Fe17.5Cr82.5/Cr/Fe strips show the transition from the "low-resistance" parallel to the "highresistance" antiparallel remanent magnetization configuration, upon increased probing current density. Quantitative comparison of the switching fields, obtained by magnetometry and magnetotransport, confirms that the Joule heating is the main mechanism responsible for the observed current-induced resistive switching.
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| 7. |
- Kravets, Anatolii, et al.
(författare)
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Current-driven thermo-magnetic switching in magnetic tunnel junctions
- 2017
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Ingår i: Applied Physics Letters. - : American Institute of Physics (AIP). - 0003-6951 .- 1077-3118. ; 111:26
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 8. |
- Kravets, Anatolii, et al.
(författare)
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Effect of nanostructure layout on spin pumping phenomena in antiferromagnet/nonmagnetic metal/ferromagnet multilayered stacks
- 2017
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Ingår i: AIP Advances. - : American Institute of Physics Inc.. - 2158-3226. ; 7:5
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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| 9. |
- Kravets, Anatolii F., et al.
(författare)
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Synthetic ferrimagnets with thermomagnetic switching
- 2014
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 90:10, s. 104427-
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Tidskriftsartikel (refereegranskat)abstract
- Interlayer exchange coupling in strong/weak/strong ferromagnetic multilayers is investigated as a function of external magnetic field and temperature, with the focus on the magnetization switching near the Curie transition in the spacer composed of a diluted ferromagnet of concentration paramagnetic in the bulk. The effect of an externally applied reversing magnetic field on the width of the thermomagnetic transition is studied experimentally and explained theoretically as a result of the interplay between the proximity-induced exchange and the Zeeman effects in the system. Of high potential for applications should be the ability to switch one of the ferromagnetic outer layers using magnetic field, temperature, or a combination of the two.
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| 10. |
- Kravets, Anatolii F., et al.
(författare)
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Temperature-controlled interlayer exchange coupling in strong/weak ferromagnetic multilayers : A thermomagnetic Curie switch
- 2012
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Ingår i: Physical Review B. Condensed Matter and Materials Physics. - 1098-0121 .- 1550-235X. ; 86:21, s. 214413-
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Tidskriftsartikel (refereegranskat)abstract
- We investigate interlayer exchange coupling based on driving a strong/weak/strong ferromagnetic trilayer through the Curie point of the weakly ferromagnetic spacer, with exchange coupling between the strongly ferromagnetic outer layers that can be switched on and off, or varied continuously in magnitude by controlling the temperature of the material. We use Ni-Cu alloys of varied composition as the spacer material and model the effects of proximity-induced magnetism and the interlayer exchange coupling through the spacer from first principles, taking into account not only thermal spin disorder but also the dependence of the atomic moment of Ni on the nearest-neighbor concentration of the nonmagnetic Cu. We propose and demonstrate a gradient-composition spacer, with a lower Ni concentration at the interfaces, for greatly improved effective-exchange uniformity and significantly improved thermomagnetic switching in the structure. The reported multilayer materials can form the base for a variety of magnetic devices, such as sensors, oscillators, and memory elements based on thermomagnetic Curie switching.
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