The effect of inserted layers on the anomalous Hall effect and perpendicular magnetic anisotropy in Ta/CoFeB/MgO heterostructures

In this work, Ta/M/CoFeB/MgO/Ta multilayers were designed to investigate the effect of M insertion on the anomalous Hall effect (AHE) and perpendicular magnetic anisotropy (PMA). Once inserted, Bi did not remain at the interface of Ta and CoFeB; it migrated to the surface of the films, which was not beneficial to PMA. X-ray photoelectron spectroscopic analyses revealed that the segregation of Ta was partly suppressed by the insertion of an Mo, Hf or Pt layer. However, the formation of a CoPt (or FePt) alloy decreased the PMA in the case of a Pt layer. The sample with Hf and Mo still exhibited a clear PMA after annealing at a 350 and 500 °C, respectively.