Anisotropy Effects on High Power Antiferromagnetic Resonance

Abstract

The AFMR frequency shift Δω in a uniaxial antiferromagnet at high power is calculated within the framework of a random phase approximation. It is shown that Δω can be expressed in terms of the number or uniform mode (k=0) magnons and degenerate (k≠0) magnons excited dynamically. The presence of these excited magnons results in a shift of the AFMR frequency through changes of the anisotropy and demagnetizing fields. In spherical samples the anisotropy induced shift is negative, so that the resonance condition for the low frequency AFMR branch for a fixed resonance frequency shifts towards lower fields.