Proposal of a Suitable Antiferromagnetic Film for Pinning Fe₃O₄ Film: CrMnPt

Abstract

Exchange coupling between half-metallic Fe₃O₄ and antiferromagnetic PtMn, MnIr, and CrMnPt films was investigated, with the goal of inducing unidirectional anisotropy in the Fe₃O₄ film, which has hard magnetic properties. The Fe₃O₄-CrMnPt system exhibited superior exchange coupling properties: a large unidirectional anisotropy constant (K_e) of -0.15 -0.18 erg/cm², a high blocking temperature (T_B) of -320°C, and a nearly unidirectionally shifted M-H curve. In the Fe₃O₄-PtMn system, the K_e value degraded to around zero. The oxygen in the Fe₃O₄ film diffused into the adjacent films through thermal annealing to produce PtMn-phase transition, resulting in considerable K_e degradation. In the Fe₃O₄ -MnIr system, the K_e and T_B values were a little too low for practical application. From these results, it is reasonable to suppose that the most suitable antiferromagnetic material for pinning Fe₃O₄ film in spintronics devices is CrMnPt.