General dispersion law in a ferromagnetic cubic magnetoelastic conductor

Abstract

A general dispersion law has been derived for a cubic, ferromagnetic, elastic, and conductive medium in which the magnetoelastic coupling and the magnetic anisotropy energy parameters can be large. Also, the direction of the external field is taken to be arbitrary and it is not assumed to be collinear with the internal field and the magnetization. Maxwell's equations and the equation of motion for the magnetization and the elastic equations of motion have been combined in a consistent manner without the assumption of collinearity of the fields to yield a general dispersion law which is of seventh order in the square of the propagation constant $\kappa$, and contains three acoustic and four magnetic branches. All of the seven values of ${\kappa }^2$ belonging to a fixed frequency and bias magnetic field have been calculated numerically by computer. The calculations are applicable to the rare-earth-transition-metal alloy systems which have large magnetic anisotropy and magnetostriction and, thus, may be useful for high-frequency magnetostrictive transducers. Also, the surface impedance is calculated for some simple field configurations.