Exchange Anisotropy Memory Effect

Abstract

A magnetic memory effect is observed in a low Curie point ferrimagnetic spinel (∼NiFe0.15Cr1.85O4) containing a coherent antiferromagnetic impurity (NiO) with a high Néel point. It is explained in terms of the Meiklejohn-Bean exchange anisotropy coupling the two phases. The past magnetic history is remembered in the spontaneous reacquisition of a fraction of the past remanent state despite prolonged storage at temperatures above the ferrimagnetic Curie point. A feature of the explanation is the condition that antiferromagnetic domains in NiO rotate irreversibly in accessible fields.