Nonlinear Effects of Crystalline Anisotropy on Ferrimagnetic Resonance

Abstract

The crystalline anisotropy of a ferrimagnetic solid will cause the magnetic resonance frequency to depend upon the angle of precession. It is shown that the resonance frequency depends quadratically upon the precession amplitude to lowest order. It is also shown that the dependence of this quadratic term upon the magnetic field orientation with respect to the crystal axis is the same as dependence of the usual zero-order resonance term upon orientation of the magnetic field. It is shown that the quadratic nonlinear term can cause a foldover of the resonance line, even in a spherical sample which is usually considered to have no foldover. The necessary conditions for the onset of this foldover are discussed, and some experimental results are mentioned.