Spontaneous resonances and universal behavior in ferrimagnets: Effective-medium theory

Publisher Website
Google Scholar
Abstract
We reconsider the high-frequency susceptibility of partially magnetized uniaxial ferrimagnets. For a demagnetized sample, effective-medium theory reproduces the exact result. Spontaneous resonances appear in a band of frequencies, in which the susceptibility follows a universal behavior. A new effect is found; a weak magnetization m ‘‘digs a hole’’ in this resonant band, of width proportional to m. The formula we propose agree with experimental data, from which microscopic parameters can be obtained. These also apply to the resistivity of a 2D conductor in a random magnetic field.