New phenomena in temperature dependence of spontaneous magnetization in a two-sublattice system

Abstract

In a two-sublattice system, it has been found that even at zero field there exist two different spin configurations, i.e., the completely parallel (or antiparallel) coupling and the canting coupling of the sublattice moments in ferromagnetic (or ferrimagnetic) materials. The present work suggests, in a phenomenological way, that the ferromagnetic canting spin configuration can show a ferrimagnetic-like temperature dependence of spontaneous magnetization. Two new types of first-order spin reorientation (FOSR) transitions are reported depending on the competition among the exchange and the anisotropies of the two sublattices. These FOSRs show an unusual behaviour that at the transition temperature both the directions and the strengths of the sublattice moments change, which are therefore defined as first-order spin reorientation reform (FOSRR).