Magnetic viscosity, quadrature susceptibility, and frequency dependence of susceptibility in single-domain assemblies of magnetite and maghemite

Néel has derived an expression relating the decay of viscous remanent magnetization and the variation of susceptibility with frequency in noninteracting single-domain assemblies of ferrimagnetic oxides, such as magnetite. This theory is extended to obtain a relationship for the quadrature susceptibility in such a sample. Measurements of these three parameters for soil samples and artificially prepared samples that contain single-domain magnetite or maghemite grains are described; the results obtained are in good agreement with theory.