Temperature Dependence of Anisotropy Energy in Antiferromagnets

The Akulov-Zener classical theory of the temperature dependence of ferromagnetic anisotropy energy is extended to the antiferromagnetic case. The result, for short-range interactions only, is that Kₙ(T)Kₙ(0)=[M(T)/M(0)]n(n+1)/2, where Kₙ(T) is the nth order anisotropy constant and $M(T)$ is the sublattice magnetization. Here, Kₙ(0) and $M(0)$ refer to the corresponding quantities at absolute zero. The result is verified by a spin-wave calculation.