Microwave polarizability of ferrite particles with non-uniform magnetization

The microwave permeability of composites made of ferrite particles in a non-magnetic matrix is affected by particle shape and size. To account for the second effect, we have developed a micromagnetic model for calculating the microwave polarizability of a particle with non-uniform magnetization. This model is described in detail: a generalized demagnetizing operator associated with the equilibrium magnetic configuration inside the particle is introduced; the polarizability is defined as the perturbation of this configuration by the external magnetic excitation; the permeability of a macroscopic sample is calculated using a space averaging procedure. The numerical methods are introduced and results for two systems are discussed: domain modes in thin films and ferrite composites with planar anisotropy.

[1]  S. Charap,et al.  Physics of magnetism , 1964 .

[2]  A. J. Freeman,et al.  Journal of Magnetism and Magnetic Materials. Volumes 198-199, 1 June 1999, , 1999 .

[3]  E. Schlömann.  Microwave Behavior of Partially Magnetized Ferrites , 1970 .

[4]  Thiaville,et al.  Horizontal Bloch lines and anisotropic-dark-field observations. , 1994, Physical review. B, Condensed matter.

[5]  R. W. Wright,et al.  Ferromagnetism at Very High Frequencies. IV. Temperature Dependence of the Magnetic Spectrum of a Ferrite , 1952 .

[6]  D. A. Dunnett.  Classical Electrodynamics , 2020, Nature.

[7]  J. Gieraltowski,et al.  Domain wall size and magnetic losses in frequency spectra of ferrites and garnets , 1977 .

[8]  J. Bouchaud,et al.  The initial susceptibility of ferrites: A quantitative theory , 1990 .

[9]  R. Fischer,et al.  Two‐ and three‐dimensional calculation of remanence enhancement of rare‐earth based composite magnets (invited) , 1994 .

[10]  A. Tonomura.  Electron-holographic interference microscopy , 1992 .

[11]  H. Gall,et al.  Influence of magnetic parameters on microwave absorption of domain mode ferromagnetic resonance , 1995 .

[12]  J. Mattei,et al.  A physical model for heterogeneous magnetic materials , 1995 .

[13]  J. Planès.  A hysteresis model with interactions , 1994 .

[14]  Mark J. Friedman.  Mathematical Study of the Nonlinear Singular Integral Magnetic Field Equation. I , 1980 .

[15]  Yasutaro Uesaka,et al.  Direct Solution of the Landau-Lifshitz-Gilbert Equation for Micromagnetics , 1989 .

[16]  H. Neal Bertram,et al.  Magnetization processes in ferromagnetic cubes , 1988 .

[17]  B. M. Fulk.  MATH , 1992 .