Voltage-controlled magnetic anisotropy in MgO/PtMnAs heterostructures

Magnesium oxide-based magnetic heterostructures with perpendicular magnetic anisotropy are receiving increasing attention for their applications in building high-density magnetic random memories. To obtain high thermal stability and flexible data writability, a large and tunable magnetic anisotropy constant (Ki) is required. In this paper, Ki is calculated for MgO/PtMnAs heterostructures with two different interfacial configurations using first-principles calculations. The MgO/AsMn_Pt heterostructure with interfacial atoms of Mn/As has a larger Ki of 4.74 mJ/m2. It is further found that a unilateral voltage-controlled magnetic anisotropy coefficient (VCMA) of 616 fJ/Vm is produced when the electric field is below - 0.2 V/nm for the MgO/AsMn_Pt heterostructure. The most significant contribution of the VCMA results from the Pt layers. The origin of these behaviors is analyzed by orbital-resolved magnetic anisotropy energy. The spin-orbit coupling of the dz2/dyz orbitals of Pt atoms is responsible for the Ki variation with voltage. This study offers a useful guide to designing magnesium oxide-based magnetic heterostructures with high and tunable magnetic anisotropy.