Giant Electric Field Modulation of Magnetism in Ferrimagnetic Heusler Heterostructures

The demand for high efficient magnetoelectric random access memory (MeRAM) requires the search of novel materials and magnetic tunnel junction stacks with voltage-controlled magnetic anisotropy (VCMA) efficiency greater than the 1000 fJ/(Vm) challenge. In this talk, we will present predictions of ab initio electronic structure calculations of the VCMA of Ir/Mn₃Ga/MgO heterostructures, in which the ultrathin ferrimagnetic Mn₃Ga has the tetragonal DO₂₂ structure. We find that the Mn_II-Mn_II- (Mn_I-Ga-) terminated interfaces exhibit large out-of-plane (in-plane) magnetic anisotropy (MA). More importantly, the calculations reveal colossal PMA and VCMA efficiency of about one order of magnitude higher than the values reported today. We demonstrate that both the MA and VCMA depend critically on the heavy metal thickness. We also predict a sign reversal of the VCMA efficiency from the Mn_II-Mn_II to the Mn_I-Ga-terminated interface. Our results show that the dominant contribution to both the PMA and VCMA arises from the strong spin-orbit-coupling of Ir and the E-field induced shift of the Ir d-derived orbitals. These findings provide useful guiding rules in the design of more energy-efficient ferrimagnetic-based MeRAM devices.