Isofrequency surfaces and dependences of electromagnetic waves in infinite ferromagnetic space

Abstract

Isofrequency surfaces and dependences of various (spin, nonresonant, and postresonant) electromagnetic waves that propagate in infinite ferromagnetic space under saturated magnetization are calculated. In a frequency interval of ω_H < ω < ω_⊥, the propagation of spin waves is characterized by open isofrequency dependences and the cutoff angles that depend on the frequency and material parameters. When the conditions are not satisfied, closed dependences are obtained. The properties of the isofrequency dependences that determine specific features of the reflection and diffraction divergence of waves are analyzed. The spin wave that propagates perpendicularly to the uniform magnetic field may exhibit zero angular width of the beam in the plane that is parallel to the magnetic field vector. In the same plane, the nonresonant wave with linear dispersion may have the diffraction divergence that is significantly less than that of the wave in isotropic media. In the presence of a plane interface, the reflection of the wave to the ferromagnetic material may give rise to two reflected beams.