Effective Parameters in Ferrimagnetic Resonance

Abstract

The steady-state solution for the susceptibility tensor of a two-sublattice system has been found by using sublattice equations of motion which include complete Landau-Lifschitz relaxation terms with individual relaxation parameters and which describe relaxation toward the instantaneous total field acting on the sublattice. It is shown that one can define effective parameters describing the behavior of the system as a whole which remain finite throughout the compensation region and, in particular, insure that the absorption coefficient will remain positive. It is also found that the effective gyromagnetic ratios characterizing the absorption and Faraday effect are different in principle, and a new term is found in the expression for the off-diagonal element which is a consequence both of the sublattice structure and total field relaxation. In the case of small damping, many of these distinctions disappear and some parameters reduce to those previously obtained. It is shown that the inclusion of total field relaxation is necessary to obtain results which are unambiguous and correct in principle; the magnetization line width product is also shown to be continuous, but vanishing at the compensation point for angular momentum.