Electric field modulation of magnetism in ferrimagnetic Heusler heterostructures

To date the realization of magnetoresistive random access memory (RAM) and magnetoelectric RAM (MeRAM) devices relies primarily on ultrathin ferromagnetic-based (FeCoB/MgO) magnetic tunnel junctions. On the other hand, the Heusler family of intermetallics is considered very promising for spintronic applications. Nevertheless, the voltage controlled magnetic anisotropy (VCMA) in ultrathin Heusler-based magnetic-tunnel junction stacks remains unexplored. Here, using the ferrimagnetic Heusler ${\mathrm{Mn}}_{3}\mathrm{Ga}$ as a prototype system, we report ab initio calculations of the electric field modulation of magnetism in the $\mathrm{Ir}/{\mathrm{Mn}}_{3}\mathrm{Ga}$/MgO heterostructure. The trilayer structures with one and three monolayer Ir caps and Mn-Mn termination exhibit large perpendicular magnetic anisotropy in contrast to those with Mn-Ga termination which yield in-plane magnetization orientation. We predict giant VCMA coefficients the magnitude and sign of which depend on both the interface termination and the Ir cap thickness. The underlying atomistic mechanism lies on the electric-field-induced shifts of the spin-orbit coupling energies of the spin-polarized $\mathrm{Ir}/d$ orbitals with different orbital angular momentum symmetries. Our paper paves the way for exploiting the unique magnetic properties of ferrimagnetic Heusler compounds for next generation MeRAM devices.