| 1. |
- 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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| 2. |
- Kravets, Anatolii, et al.
(författare)
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Spin dynamics in a Curie-switch
- 2015
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Ingår i: Journal of Physics. - : Institute of Physics (IOP). - 0953-8984 .- 1361-648X. ; 27:44
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Tidskriftsartikel (refereegranskat)abstract
- Ferromagnetic resonance properties of F-1/f/F-2/AF multilayers, where weakly ferromagnetic spacer f is sandwiched between strongly ferromagnetic layers F-1 and F-2, with F-1 being magnetically soft and F-2-magnetically hard due to exchange pinning to antiferromagnetic layer AF, are investigated. Spacer-mediated exchange coupling is shown to strongly affect the resonance fields of both F-1 and F-2 layers. Our theoretical calculations as well as measurements show that the key magnetic parameters of the spacer, which govern the ferromagnetic resonance in F-1/f/F-2/AF, are the magnetic exchange length (Lambda), effective saturation magnetization at T = 0 (m(0)) and effective Curie temperature (T-C(eff)). The values of these key parameters are deduced from the experimental data for multilayers with f = NixCu100-x, for the key ranges in the Ni-concentration (x = 54 divided by 70 at. %) and spacer thickness (d = 3 divided by 6 nm). The results obtained provide a deeper insight into thermally-controlled spin precession and switching in magnetic nanostructures, with potential applications in spin-based oscillators and memory devices.
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| 3. |
- 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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| 4. |
- 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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| 5. |
- 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: Fizika Nizkih Temperatur. - : Institute for Low Temperature Physics and Engineering. - 0132-6414 .- 1816-0328. ; 42:9, s. 972-980
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Tidskriftsartikel (refereegranskat)abstract
- The work carries out a comprehensive analysis of magnetic resonance properties of F1/f(d)/F2pin multilayers, where F1 and F2pin are soft and hard magnetic layers and f is a weakly magnetic spacer with the Curie Curie temperature in the vicinity of room temperature. Depending on the magnetic state of the spacer, ferromagnetic or paramagnetic, the exchange interaction between F1 and F2pin becomes a function of temperature which is attractive for a number of applications. Our results show that the interlayer exchange coupling can be enhanced either by decreasing the spacer thickness, d, or lowering temperature. Stronger exchange coupling results in stronger unidirectional anisotropy of the ferromagnetic resonance in F1, as well as in atypical for thin films broadening of the resonance line. The observed behavior was analyzed taking into account two effects of different character - variable spacer thickness d and variable temperature. It is shown that the changes in the unidirectional anisotropy of the FMR spectra have a similar dependence on d and temperature. On the contrary, the FMR line broadening due to magnetization relaxation in the system is significantly affected by the changes in the interlayer exchange interaction on varying d, and is only slightly affected by the changes in temperature.
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| 6. |
- Cherepov, Sergiy, et al.
(författare)
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Resonant Activation of a Synthetic Antiferromagnet
- 2011
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Ingår i: Physical Review Letters. - 0031-9007 .- 1079-7114. ; 107:7, s. 077202-
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Tidskriftsartikel (refereegranskat)abstract
- The magnetic decay time of a synthetic antiferromagnet comprised of two closely spaced magnetic dipoles is measured in the presence of microwave excitation. The system is known to be highly stable with respect to switching between its two antiparallel ground states under quasistatic magnetic fields. We show that an order of magnitude lower field can switch the pair, provided the field is applied in resonance with the optical eigenmode of the collective spin dynamics in the system. We furthermore show that thermal agitation can play an essential role in spin-flop switching for resonant excitations of near-or subcritical amplitude.
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| 7. |
- Dzhezherya, Yu. I., et al.
(författare)
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Kapitza problem for the magnetic moments of synthetic antiferromagnetic systems
- 2012
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 115:2, s. 284-288
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Tidskriftsartikel (refereegranskat)abstract
- The dynamics of magnetization in synthetic antiferromagnetic systems with the magnetic dipole coupling in a rapidly oscillating field has been examined. It has been revealed that the system can behave similar to the Kapitza pendulum. It has been shown that an alternating magnetic field can be efficiently used to control the magnetic state of a cell of a synthetic antiferromagnet. Analytical relations have been obtained between the parameters of such an antiferromagnet and an external magnetic field at which certain quasistationary states are implemented.
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| 8. |
- Dzhezherya, Yu I., et al.
(författare)
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Remagnetization of synthetic antiferromagnetic cells by a magnetic field pulse
- 2013
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Ingår i: Journal of Experimental and Theoretical Physics. - 1063-7761 .- 1090-6509. ; 117:6, s. 1059-1065
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Tidskriftsartikel (refereegranskat)abstract
- The theory of the dynamic remagnetization of a synthetic antiferromagnetic system and magnetic points located on a magnetic substrate in an external magnetic field has been considered. The energies of the equilibrium states of the system have been calculated. The conditions of switching between equilibrium states have been described. The conditions of applicability of this theory have been formulated. It has been shown that the process of remagnetization can be implemented in an inertialess regime, escaping the long-term relaxation of the system to a new equilibrium position with the use of a special shape of the field signal. The possibility of the reduction of the switching field amplitude by varying the pulse duration has been demonstrated.
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| 9. |
- Koop, Björn C., et al.
(författare)
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Demonstration of bi-directional microwave-assisted magnetic reversal in synthetic ferrimagnets
- 2013
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Ingår i: Applied Physics Letters. - : AIP Publishing. - 0003-6951 .- 1077-3118. ; 103:14, s. 142408-
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Tidskriftsartikel (refereegranskat)abstract
- We study spin dynamics in synthetic ferrimagnets, in which two dipole-coupled magnetic nanoparticles are different in thickness or biased asymmetrically with an external field. We observe a splitting of the optical spin-resonance for the two antiparallel ground states of the system and demonstrate how this splitting can be used to deterministically select a particular ground state. The demonstrated resonant switching is a fast and low-field way of controlling the magnetic state of nanodevices currently used in such large scale applications as magnetic random access memory.
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