Anatomy of Voltage-Controlled Magnetic Anisotropy in Heterostructures with Atomically-Thin Heavy Metals*

The demand for higher speed, higher density, and more energy-efficient magnetoelectric random access memory (MeRAM) requires the urgent search of novel materials and magnetic tunnel junction with voltage-controlled magnetic anisotropy (VCMA) efficiency greater than 1000 fJ/(Vm). Employing ab initio electronic structure calculations we propose a MgO/X/FeCo/MgO heterostructure, where X is an atomically-thin late transition metal (Ir, Pt, Rh), which exhibits both giant perpendicular magnetic anisotropy (PMA) and VCMA efficiency, where the former (latter) is one (one to two) order of magnitude higher than the values reported to date. We demonstrate that the dominant contribution to both the PMA and VCMA arises from the heavy metal X due to the large biaxial tensile strain-induced magnetism in X. These findings provide useful guiding rules in exploiting the large SOC and biaxial tensile strain-induced magnetism in the late transition metals for the design of the next-generation of ultra-low energy MeRAM devices.