Ta cap-induced stabilization of interfacial ferromagnetism and enhanced magnetoelectricity in ultrathin FeRh films

We report ab initio electronic structure calculations to study the effect of Ta cap on the magnetic properties and the magnetoelectric response of Ta/FeRh/MgO nanojunctions. The calculations reveal that the Ta cap reverses the magnetic phase stability in ultrathin FeRh films leading to the stabilization of the ferromagnetic phase and interfacial reconstructed ferromagnetism. We demonstrate that the Ta cap induces a large charge transfer which in turn reduces dramatically the magnetic moments of the interfacial Fe atoms regardless the magnetic configuration and enhances the in-plane (out-of-plane) magnetization orientation of the antiferromagnetic (AFM) (ferromagnetic (FM)) phase compared to the uncapped bilayer. The Ta cap modifies substantially and enhances the magnetoelectric response under an external electric field, where the voltage controlled magnetic anisotropy (VCMA) changes from $\vee$-shape in the AFM to linear behavior in the FM phase with large VCMA efficiency. These findings demonstrate the manipulation of magnetic ordering of FeRh films with heavy metal capping and electric field which can promote the application of FeRh alloy in MeRAM.