Grain-size dependence of magnetic microstructure and high-frequency susceptibility of nanocrystalline thin films: A micromagnetic simulation study

•Grain size is a key parameter determining magnetic properties of nanocrystalline films.•Stochastic magnetic structure—magnetization ripple—is formed in such films.•If grain exceeds critical size, FMR line broadening occurs at certain frequencies.•Effects are caused by two-magnon scattering of spin...

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Bibliographic Details
Published in:Journal of magnetism and magnetic materials 2021-07, Vol.529, p.167856, Article 167856
Main Authors: Izotov, A.V., Belyaev, B.A., Solovev, P.N., Boev, N.M.
Format: Article
Language:English
Subjects:
Crystallites
Ferromagnetic resonance
Ferromagnetism
Grain size
Local magnetic anisotropy
Magnetic films
Magnetic structure
Magnetization
Magnetization ripple
Magnons
Micromagnetic simulation
Microstructure
Nanocrystallites
Nanocrystals
Resonance lines
Ripples
Scattering
Simulation
Thin films
Two-magnon scattering process
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Summary:•Grain size is a key parameter determining magnetic properties of nanocrystalline films.•Stochastic magnetic structure—magnetization ripple—is formed in such films.•If grain exceeds critical size, FMR line broadening occurs at certain frequencies.•Effects are caused by two-magnon scattering of spin waves on magnetization ripple. The size of crystallites is one of the most important factors that determine the key characteristics of nanocrystalline thin magnetic films that make them very promising media for various applications. In this paper, using micromagnetic simulation, we study in detail the influence of the grain size on the magnetic microstructure of the films and its relation with high-frequency dynamics of magnetization. When the grain size exceeds some critical value Dcr, a sharp broadening and shift of the ferromagnetic resonance line are observed at certain frequencies of the alternating magnetic field. Using a two-magnon scattering model, it is shown that these effects are caused by the scattering of spin waves on the inhomogeneous stochastic magnetic structure—magnetization ripple. An expression for the determination of the critical size Dcr is obtained. The micromagnetic simulation results agree with the main conclusions of the static and dynamic theories of magnetization ripple and also confirmed by experimental data reported by other authors.
ISSN:0304-8853
1873-4766
DOI:10.1016/j.jmmm.2021.167856