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Search Results: 1 - 10 of 2743 matches for " Mikhail Kostylev "
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Asymmetry of modal profiles of dipole-exchange spin waves in thin high-magnetic moment metallic ferromagnetic films
Mikhail Kostylev
Physics , 2012,
Abstract: The asymmetry of the modal profiles for dipole-exchange spin waves propagating in in-plane magnetized ferromagnetic films at a right angle to the applied magnetic field has been investigated theoretically. It was found that in the large-magnetic moment ferromagnetic metallic films with typical thicknesses 10-60 nm the fundamental mode of the spectrum is localized at the surface opposite to the surface of localization of the exchange-free Damon-Eshbach surface wave. This anomalous localization of the wave does not affect the non-reciprocity of spin wave excitation by microstrip and coplanar transducers but may be detected in other types of experiments.
Coupling of microwave magnetic dynamics in thin ferromagnetic films to stripline transducers in the geometry of the broadband stripline ferromagnetic resonance
Mikhail Kostylev
Physics , 2015,
Abstract: We constructed a quasi-analytical self-consistent model of the stripline-based broadband ferromagnetic resonance (FMR) measurements of ferromagnetic films. Exchange-free description of magnetization dynamics in the films allowed us to obtain simple analytical expressions. They enable quick and efficient numerical simulations of the dynamics. With this model we studied the contribution of radiation losses to the ferromagnetic resonance linewidth, as measured with the stripline FMR. We found that for films with large conductivity of metals the radiation losses are significantly smaller than for magneto-insulating films. Excitation of microwave eddy currents in these materials contributes to the total microwave impedance of the system. This leads to impedance mismatch with the film environment resulting in decoupling of the film from the environment and, ultimately, to smaller radiation losses. We also show that the radiation losses drop with an increase in the stripline width and when the sample is lifted up from the stripline surface. Hence, in order to eliminate this measurement artifact one needs to use wide striplines and introduce a spacer between the film and the sample surface. The radiation losses contribution is larger for thicker films.
A rigorous two-dimensional model for the stripline ferromagnetic resonance response of metallic ferromagnetic films
Zhuonan Lin,Mikhail Kostylev
Physics , 2014, DOI: 10.1063/1.4907535
Abstract: In this work we constructed a two-dimensional numerical model for calculation of the stripline ferromagnetic resonance (FMR) response of metallic ferromagnetic films. We also conducted numerical calculations by using this software. The calculations demonstrated that the eddy current contribution to the FMR response decreases with a decrease in the stripline width. The most important manifestations of the conductivity (eddy current) effect are excitation of the higher-order standing spin waves across the film thickness in the materials for which the standing spin wave peaks would be absent in cavity FMR measurements and strong dependence of the off-resonance series conductance of the stripline on the stripline width. Whereas the contribution of the eddy currents to the stripline FMR response can be very significant, because wide striplines (100nm+) are conventionally used for the FMR measurements, it is negligible in the case of excitation of spin waves, just because very narrow stripline transducers (0.5-5micron wide) are required in order to excite spin waves in metallic ferromagnetic films in a noticeable frequency/applied field range.
Multifrequency transverse Faraday effect in single magneto-dielectric microspheres
Ivan S. Maksymov,Mikhail Kostylev
Physics , 2014,
Abstract: We propose using a single magneto-dielectric microsphere as a device for enhancing the transverse Faraday effect at multiple wavelengths at the same time. Although the diameter of the sphere can be $<1$ $\mu$m, the numerically predicted strength of its magneto-optical (MO) response can be an order of magnitude stronger than in MO devices based on thick magnetic plates. The MO response of a microsphere is also comparable with that of subwavelength magneto-dielectric gratings which, however, operate at a single wavelength and occupy a large area. In contrast to gratings and thick plates, the compact size of the microsphere and its capability to support spin-wave excitations make it suitable for applications in nanophotonics, imaging systems, and magnonics.
Extremely high-resolution measurements of microwave magnetisation dynamics in magnetic thin films and nanostructures
Eugene N. Ivanov,Mikhail Kostylev
Physics , 2014,
Abstract: In this work we discuss the use of interferometric measurement technique to study microwave magnetization dynamics on ferromagnetic nanostructures. We demonstrate that in this way one can resolve features which are impossible to resolve with broadband ferromagnetic resonance and traveling spin wave spectroscopy otherwise.
Impact of eddy currents on the dispersion relation of surface spin waves in thin conducting magnetic films
Ivan S. Maksymov,Mikhail Kostylev
Physics , 2013, DOI: 10.1088/0022-3727/46/49/495001
Abstract: We propose a rigorous solution to a long-standing problem of the impact of eddy currents on the dispersion relation of surface spin waves propagating in thin conducting magnetic films. Our results confirm the prediction of the Almeida-Mill's exchange-free theory that the inclusion of the eddy current contribution results in a deviation of the dispersion curve for the fundamental mode from the Damon-Eshbach law and a substantial linewidth broadening in a large wave vector range. We show that the decrease in the spin wave frequency is due to an increase in the in-plane component of the dynamic magnetic field within the conducting film. The decrease in the frequency is accompanied by a drastic change in the asymmetry of the modal profiles for the waves. This effect is not observable in magneto-insulating films and therefore it is unambiguously attributed to eddy currents that appear in conducting films only. We also show that the wave vector range in which eddy currents affect the dispersion curve is strongly correlated with the value of the film conductivity. This result holds for conducting films with the thickness 10-100 nm, which are considered promising for future magnonic and spintronic applications.
Effect of disorder studied with ferromagnetic resonance for arrays of tangentially magnetized sub-micron Permalloy discs fabricated by nanosphere lithography
Nils Ross,Mikhail Kostylev,Robert L. Stamps
Physics , 2010, DOI: 10.1063/1.3526307
Abstract: Tangentially magnetized trigonal arrays of sub-micron Permalloy discs are characterized with ferromagnetic resonance to determine the possible contributions to frequency and linewidth from array disorder. Each array is fabricated by a water-surface self-assembly lithographic technique, and consists of a large trigonal array of 700 nm diameter magnetic discs. Each array is characterized by a different degree of ordering. Two modes are present in the ferromagnetic resonance spectra: a large amplitude, `fundamental' mode and a lower amplitude mode at higher field. Angular dependence of the resonance field in a very well ordered array is found to be negligible for both modes. The relationship between resonance frequency and applied magnetic field is found to be uncorrelated with array disorder. Linewidth is found to increase with increasing array disorder.
Transverse magneto-optical Kerr effect in subwavelength dielectric gratings
Ivan S. Maksymov,Jessica Hutomo,Mikhail Kostylev
Physics , 2014, DOI: 10.1364/OE.22.008720
Abstract: We demonstrate theoretically a large transverse magneto-optical Kerr effect (TMOKE) in subwavelength gratings consisting of alternating magneto-insulating and nonmagnetic dielectric nanostripes. The reflectivity of the grating reaches $96\%$ at the frequencies corresponding to the maximum of the TMOKE response. The combination of a large TMOKE response and high reflectivity is important for applications in $3$D imaging, magneto-optical data storage, and magnonics.
Metallic spintronic nanofilm as a hydrogen sensor
Crosby S. Chang,Mikhail Kostylev,Eugene Ivanov
Physics , 2013, DOI: 10.1063/1.4800923
Abstract: We investigate the response of palladium-cobalt bi-layer thin films to hydrogen charging at atmospheric pressure for spintronic applications. We find that hydrogen absorption by the palladium layer results in the narrowing and shifting of the ferromagnetic resonance line for the material. We explain the observed phenomena as originating from reduction in spin pumping effect and from variation in the magnetic anisotropy of the cobalt film through an interface effect. The shift of the resonance frequency or field is the easiest to detect. We utilize it to demonstrate functionality of the bi-layer films as a hydrogen sensor.
Rigorous numerical study of strong microwave photon-magnon coupling in all-dielectric magnetic multilayers
Ivan S. Maksymov,Jessica Hutomo,Donghee Nam,Mikhail Kostylev
Physics , 2015, DOI: 10.1063/1.4921535
Abstract: We demonstrate theoretically a strong local enhancement of the intensity of the in-plane microwave magnetic field in multilayered structures made from a magneto-insulating yttrium iron garnet (YIG) layer sandwiched between two non-magnetic layers with a high dielectric constant matching that of YIG. The enhancement is predicted for the excitation regime when the microwave magnetic field is induced inside the multilayer by the transducer of a stripline Broadband Ferromagnetic Resonance (BFMR) setup. By means of a rigorous numerical solution of the Landau-Lifshitz-Gilbert equation consistently with the Maxwell's equations, we investigate the magnetisation dynamics in the multilayer. We reveal a strong photon-magnon coupling, which manifests itself as anti-crossing of the ferromagnetic resonance (FMR) magnon mode supported by the YIG layer and the electromagnetic resonance mode supported by the whole multilayered structure. The frequency of the magnon mode depends on the external static magnetic field, which in our case is applied tangentially to the multilayer in the direction perpendicular to the microwave magnetic field induced by the stripline of the BFMR setup. The frequency of the electromagnetic mode is independent of the static magnetic field. Consequently, the predicted photon-magnon coupling is sensitive to the applied magnetic field and thus can be used in magnetically tuneable metamaterials based on simultaneously negative permittivity and permeability achievable thanks to the YIG layer. We also suggest that the predicted photon-magnon coupling may find applications in microwave quantum information systems.
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