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| 2. |
- Polishchuk, Dmytr, et al.
(författare)
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Temperature and thickness dependent magnetostatic properties of [Fe/Py]/FeMn/Py multilayers
- 2021
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : AIP Publishing. - 1063-777X .- 1090-6517. ; 47:6, s. 483-487
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic properties of thin-film multilayers [Fe/Py]/FeMn/Py are investigated as a function of temperature and thickness of the antiferromagnetic FeMn spacer using SQUID magnetometry. The observed behavior differs substantially for the structures with 6 nm and 15 nm FeMn spacers. While the 15 nm FeMn structure exhibits exchange pinning of both ferromagnetic layers in the entire measurement temperature interval from 5 to 300 K, the 6 nm FeMn structure becomes exchange de-pinned in the vicinity of room temperature. The depinned state is characterized by a single hysteresis loop centered at zero field and having enhanced magnetic coercivity. The observed properties are explained in terms of finite-size effects and possible ferromagnetic interlayer coupling through the thin antiferromagnetic spacer.
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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. |
- 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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| 5. |
- Kravets, A. F., et al.
(författare)
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Exchange-induced phase separation in Ni-Cu films
- 2012
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Ingår i: Journal of Magnetism and Magnetic Materials. - : Elsevier BV. - 0304-8853 .- 1873-4766. ; 324:13, s. 2131-2135
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Tidskriftsartikel (refereegranskat)abstract
- Magneto-structural properties of films of diluted ferromagnetic alloys NixCu1-x in the concentration range 0.7 < x < 1.0 are studied experimentally. Films deposited by magnetron sputtering show partial phase separation, as evidenced by structural analysis and ferromagnetic resonance measurements. The phase diagram of the NixCu1-x bulk system is obtained using numerical theoretical analysis of the electronic structure, taking into account the interatomic exchange interactions. The results confirm the experimentally found partial phase separation, explain it as magnetic in origin, and indicate an additional metastable region connected with the ferromagnetic transition in the system.
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| 6. |
- Kravets, A. F., et al.
(författare)
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Anisotropic magnetization relaxation in ferromagnetic multilayers with variable interlayer exchange coupling
- 2016
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Ingår i: PHYSICAL REVIEW B. - : American Physical Society. - 2469-9950. ; 94:6
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Tidskriftsartikel (refereegranskat)abstract
- The ferromagnetic resonance (FMR) linewidth and its anisotropy in F-1/f/F-2/AF multilayers, where spacer f has a low Curie point compared to the strongly ferromagnetic F-1 and F-2, is investigated. The role of the interlayer exchange coupling in magnetization relaxation is determined experimentally by varying the thickness of the spacer. It is shown that stronger interlayer coupling via thinner spacers enhances the microwave energy exchange between the outer ferromagnetic layers, with themagnetization of F-2 exchange dragged by the resonance precession in F-1. A weaker mirror effect is also observed: the magnetization of F-1 can be exchange dragged by the precession in F-2, which leads to antidamping and narrower FMR linewidths. A theory is developed to model the measured data, which allows separating various contributions to the magnetic relaxation in the system. Key physical parameters, such as the interlayer coupling constant, in-plane anisotropy of the FMR linewidth, and dispersion of the magnetic anisotropy fields, are quantified. These results should be useful for designing high-speed magnetic nanodevices based on thermally assisted switching.
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| 7. |
- 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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| 8. |
- Polishchuk, Dmytr, et al.
(författare)
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Antiferromagnet-mediated interlayer exchange : Hybridization versus proximity effect
- 2023
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Ingår i: Physical Review B. - : American Physical Society (APS). - 2469-9950 .- 2469-9969. ; 107:22
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Tidskriftsartikel (refereegranskat)abstract
- We investigate the interlayer coupling between two thin ferromagnetic (F) films mediated by an antiferromagnetic (AF) spacer in F∗/AF/F trilayers and show how it transitions between different regimes on changing the AF thickness. Employing layer-selective Kerr magnetometry and ferromagnetic-resonance techniques in a complementary manner enables us to distinguish between three functionally distinct regimes of such ferromagnetic interlayer coupling. The F layers are found to be individually and independently exchange-biased for thick FeMn spacers - the first regime of no interlayer F-F∗ coupling. F-F∗ coupling appears on decreasing the FeMn thickness below 9 nm. In this second regime found in structures with 6.0-9.0-nm-thick FeMn spacers, the interlayer coupling exists only in a finite temperature interval just below the effective Néel temperature of the spacer, which is due to magnon-mediated exchange through the thermally softened antiferromagnetic spacer, vanishing at lower temperatures. The third regime, with FeMn thinner than 4 nm, is characterized by a much stronger interlayer coupling in the entire temperature interval, which is attributed to a magnetic-proximity induced ferromagnetic exchange. These experimental results, spanning the key geometrical parameters and thermal regimes of the F∗/AF/F nanostructure, complemented by a comprehensive theoretical analysis, should broaden the understanding of the interlayer exchange in magnetic multilayers and potentially be useful for applications in spin thermionics.
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| 9. |
- Polishchuk, Dmytr, et al.
(författare)
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Ferromagnetic resonance in nanostructures with temperature-controlled interlayer interaction
- 2016
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Ingår i: Low temperature physics (Woodbury, N.Y., Print). - : American Institute of Physics (AIP). - 1063-777X .- 1090-6517. ; 42:9, s. 761-767
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Tidskriftsartikel (refereegranskat)abstract
- 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.
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