First-Principles Study of Electric Field Effects on the Magnetic Anisotropy in MgO/Fe₂IrGa Heterostructures

The applications of voltage-torque magnetic random access memory are critically dependent on the substantial voltage-controlled magnetic anisotropy (VCMA) effect. In this study, first-principles calculations are employed to explore the impact of electric fields on the magnetic anisotropy (MA) in a heterostructure composed of insulator, MgO, and Heusler alloy, Fe₂IrGa. Our findings reveal that the MgO/Fe₂IrGa heterostructure terminated with Fe and Ir atoms exhibits strong perpendicular MA and a large VCMA coefficient of − 1959 fJ/Vm. The Ir atoms located at the surface and interface regions of the heterostructure have been identified as the primary contributors to the observed large VCMA coefficient. Their response to applied voltages plays a crucial role in determining the overall magnetic anisotropy of the system. Second-order perturbation theory and orbital-resolved MA are used to gain insight into the causes of these behaviors. Essentially, the VCMA effect is primarily attributed to the hybridization of d_yz and d_z2 orbitals near the Fermi level in Ir atoms located at the interface and surface of the heterojunction under the applied electric field.