Temperature‐Driven Spin Reorientation Transition in CoPt/AlN Multilayer Films

Abstract

Spin reorientation transition phenomena from out‐of‐plane to in‐plane direction with increasing temperature are observed for the 500°C annealed CoPt/AlN multilayer films with different CoPt layer thicknesses. CoPt‐AlN interface and volume anisotropy contributions, favoring out‐of‐plane and in‐plane magnetization, respectively, are separately determined at various temperatures. Interface anisotropy exhibits much stronger temperature dependence than volume contribution, hence the temperature‐driven spin reorientation transition occurs. Interface anisotropy in this work consists of Néel interface anisotropy and magnetoelastic effect. Magnetoelastic effect degrades rapidly and changes its sign from positive to negative above 200°C, because of the involvement of stress state in CoPt films with temperature. By contrast, Néel interface anisotropy decays slowly, estimated from a Néel mean field model. Thus, the strong temperature dependence of CoPt‐AlN interface anisotropy is dominated by the change of magnetoelastic effect.