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

摘要

The voltage-controlled magnetic anisotropy (VCMA) effect in a 3d-transition ultrathin ferromagneticlayer is attracting much attention as a promising approach of ultra-low spin manipulation for futurespintronic devices, such as voltage-torque MRAM [1]. However, to show the scalability of voltage-torqueMRAM, we need a sufficiently high VCMA coefficient, for example, 200-500 fJ/Vm for cache memoryand 500-2000 fJ/Vm for main memory applications. However, the demonstrations of high-speed VCMAeffect 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 5dheavy metal iridium (Ir) to enhance the VCMA effect and found that low concentration of Ir doping in anultrathin Fe layer is effective to achieve the enhanced interfacial PMA with large VCMA coefficient over300 fJ/Vm [3].