The effect of the Ta spacer on the interfacial microstructures and magnetic properties of MTJs with double MgO-barrier

We investigated the effect that Ta spacer had on the interfacial microstructures and magnetic properties of MgO/CoFeB/Ta/CoFeB/MgO films. We found that when the Ta spacer thickness was optimized, the double MgO interface led to an enhancement in the perpendicular magnetic anisotropy (PMA) and thermostability. By systematically studying the changes for different structures in the chemical state, we interpreted how elements diffuse and alter the chemical states and properties of the magnetic tunnel junctions (MTJs). We found that increasing the Fe oxide is crucial to the PMA in the films and we attribute the increase in the of Fe oxide content to the oxygen liberated by the reduction of boron oxide. •The magnetic properties and thermal stability of MgO/CoFeB/Ta/CoFeB/MgO films were studied.•Fe oxide was increased through the oxygen liberated by the reduction of boron oxide.•The formation of minor Fe(Co)oxide at the CoFeB/MgO interface enhanced the PMA.