Theory of Antiferromagnetism and Antiferromagnetic Resonance Absorption, I

Abstract

It will be pointed out that the anisotropy energy is of primary importance in the theory of antiferromagnetism. The formula for the susceptibility x=(:;(ll +2x..t_)/3, which follows in van Vleck's theory from a rather arbitrary assumption that the parallel and perpendicular domains are distributed with a ratio 1:2, can only be justified by inclusion of anisotropy energy. Formula for the dependency of the susceptibility upon external magnetic field will be derived and it will be shown that the field-dependent part varies proportional to the square of the intensity of the magnetic field, and inversely proportional to the anisotropy constant.