Enhanced interfacial perpendicular magnetic anisotropy and voltage-controlled magnetic anisotropy in iridium-doped Fe/MgO structures

摘要

The voltage-controlled magnetic anisotropy (VCMA) effect in a 3d-transition ultrathin ferromagnetic layer is attracting much attention as a promising approach of ultra-low spin manipulation for future spintronic devices, such as voltage-torque MRAM [1]. However, to show the scalability of voltage-torque MRAM, we need a sufficiently high VCMA coefficient, for example, 200-500 fJ/Vm for cache memory and 500-2000 fJ/Vm for main memory applications. However, the demonstrations of high-speed VCMA effect in magnetic tunnel junction (MTJ) devices are limited to be about 100 fJ/Vm at present. In this work, following the prediction by first-principles calculation [2], we tried the interface engineering using 5d heavy metal iridium (Ir) to enhance the VCMA effect and found that low concentration of Ir doping in an ultrathin Fe layer is effective to achieve the enhanced interfacial PMA with large VCMA coefficient over 300 fJ/Vm [3].