Published online by Cambridge University Press: 27 February 2015
We study W | Ta | CoFeB | MgO stacks for spin-orbit torque MRAM applications. A strong perpendicular magnetic anisotropy is obtained after annealing for CoFeB layer thickness of 0.9 nm or 1.2 nm and for specific W/Ta ratios, were the Ta layer thickness is between 0.3 nm and 1 nm. Furthermore, the desired high-spin orbit coupling β-phase of W is preserved even after annealing at 350°C. We argue that an efficient B getter, like Ta, is necessary for the coherent crystallization of the CoFeB | MgO interface that allows for the establishment of perpendicular magnetic anisotropy.