Micromagnetic Analysis of Edge Effects in a Thin Magnetic Film during Local Excitation of Magnetization Oscillations
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Russian Physics Journal, Vol. 63, No. 5, September, 2020 (Russian Original No. 5, May, 2020)
PHYSICS OF MAGNETIC PHENOMENA MICROMAGNETIC ANALYSIS OF EDGE EFFECTS IN A THIN MAGNETIC FILM DURING LOCAL EXCITATION OF MAGNETIZATION OSCILLATIONS B. A. Belyaev,1,2 A. V. Izotov,1,2 G. V. Skomorokhov,1 P. N. Solovev1,2
UDC 537.622
The method of numerical micromagnetic simulation was used to study the magnetization dynamics of a thin film with uniaxial magnetic anisotropy during ferromagnetic resonance (FMR) excitation in it on the local sites by a linearly polarized high-frequency magnetic field emitted from the 1 mm opening in the metallic screen of the transmission line. It was established that non-uniformities of demagnetizing fields emerging near the film edges lead not only to the change in the FMR field, but also to the change in the value and direction of the uniaxial anisotropy field. The distribution of non-uniformities of the magnetic anisotropy characteristics over the area of 60 nm thick permalloy film that was measured on the scanning FMR spectrometer agrees well with the micromagnetic simulation results. Demagnetizing fields were proved to be the main cause for the edge effects in magnetic films. Keywords: micromagnetic simulation, thin magnetic film, edge effects, ferromagnetic resonance, magnetic anisotropy.
INTRODUCTION It is well known that thin-film magnetic structures have a number of unique physical properties that distinguish them from bulk magnetic materials. For instance, thanks to their microstructure, thin nanocrystalline magnetic films demonstrate high magnetic susceptibility and low losses at microwave frequencies [1], which makes them promising media to be used in high-frequency sensors of weak magnetic fields and signal processing devices [2, 3]. Obviously, characteristics of any devices based on magnetic films depend on the uniformity of magnetic parameter distribution over the sample surface, but devices where magnetic films are under condition of uniform ferromagnetic resonance (FMR) [4] are especially susceptible to non-uniformity. As far as film samples in devices have finite dimensions, even when they are magnetized by a uniform magnetic field in the plane the demagnetizing field created by ‘magnetic charges’ on the sample edges [5] will be non-uniform. As a rule, in thin magnetic films, spatial non-uniformity of the demagnetizing field on the edges is taken into account only when sample dimensions become comparable with their thickness. In such samples, magnetostatic oscillation modes with a finite wavelength [6, 7] may be excited under the impact of the uniform high-frequency field, and interesting features associated with oscillation localization near their edges are also observed [8, 9]. Nevertheless, as will be shown in this paper, huge values of demagnetizing fields existing on the edges of permalloy films have considerable impact on the integral magnetic characteristics even in those samples the dimensions
1
L.V. Kirensky Institute of Physics, Krasnoyarsk Scientific Center, S
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