Abstract
The magnetic permeability is generally a second-rank tensor for an anisotropic medium. By considering a dc bias magnetic field and an ac circularly polarized wave, a generalized permeability can be derived. The formula for the generalized permeability explains why most dielectrics, paramagnetic and diamagnetic materials, and even metals have a relative permeability close to unity. For ferromagnetic or ferrimagnetic materials, the permeability strongly depends on the applied magnetic field and the polarizations of the electromagnetic waves. This work discusses how a circularly polarized wave interacts with the magnetic dipole moment being induced by and precessing around the applied dc bias field. The gyromagnetic resonance between the wave and the induced dipole allows us to find a condition where the incident wave can propagate through the medium without reflection. This explains the mysterious effect of gyromagnetically induced transparency.