Impact of Ta Diffusion on the Perpendicular Magnetic Anisotropy of Ta/CoFeB/MgO

Effects of Ta diffusion on the perpendicular magnetic anisotropy (PMA) of Ta/Co
_0.6
Fe
_0.2
B
_0.2
(12.5 Å)/MgO stacks were investigated. We found that Ta initially mixed with Co
_0.6
Fe
_0.2
B
_0.2
and its diffusion became prominent above 300 °C. Initial diffusion of Ta into the Co
_0.6
Fe
_0.2
B
_0.2
was not detrimental to the PMA, but a significant PMA reduction occurred when Ta migrated to the Co
_0.6
Fe
_0.2
B
_0.2
/MgO interface. This accounts for the fact that optimizing the PMA of Ta/CoFeB/MgO requires the tuning of both CoFeB thickness and annealing temperature.