EXCHANGE ANISOTROPY OF Co-CoO PERPENDICULAR MAGNETIC FILMS

Abstract

Hysteresis loops perpendicular to the film plane of Co-CoO perpendicular magnetic films have been measured at various temperatures, and the temperature dependence of both the unidirectional and the uniaxial exchange anisotropy have been investigated. Alao the existence of these two types of exchange anisotropies and their influence on the magnetic properties of thin films are shown by torque curves measured at room and lower temperatures. By comparing the changes in some quantities (The amount of vertical magnetization (Mr⊥/Mr"), relative increment of hysteresis loop half-wlidths [(fHc-rHc)/2-Hc]/Hc and the ratio values of loop shift to vertical coercivity [(fHc+rHc)/2]/Hc) in several samples as the oxygen content is varied, we infer that the existence of antiferromagnetic CoO is necessary for the occurrence of exchange anisotropy, and a perpendicular magnetic ordering of the spin magnetic moments of the hcp Co atoms is an origin causing the uniaxial property of exchange anisotropy in the films.