Underlayer material influence on electric-field controlled perpendicular magnetic anisotropy in CoFeB/MgO magnetic tunnel junctions

We study the dependence of the perpendicular magnetic anisotropy on the underlayer material in magnetic tunnel junction. Using several different 4d and 5d metals we identify an optimal seed layer in terms of high anisotropy, low mixing, and high thermal stability. In such systems we investigate the tunability of the anisotropy by means of electric fields. Especially, by using W as the underlayer of the CoFeB/MgO/CoFeB trilayer we could obtain good thermal stability that allows for annealing in the temperatures up to $450{\phantom{\rule{0.16em}{0ex}}}^{\ensuremath{\circ}}\mathrm{C}$, which results in high perpendicular anisotropy.