Perpendicular magnetic anisotropy in TbFeCo/MgO structure with Ta- and Hf-underlayer

Abstract In this study, the interfacial PMA in (Ta or Hf)/TbFeCo/MgO/Ta structures are investigated and the effectiveness of two kinds of heavy-metal Hf and Ta underlayers are explored. The PMA of TbFeCo is found to critically rely on several aspects like Tb-concentration (Tb sputtering power), underlayer material (Ta/Hf), annealing temperature and heating rate of annealing. The crystalline phase of the underlayer is investigated by XRD and resistivity measurements and optimized by changing the film thickness. It was observed that for the Hf underlayer the PMA could be obtained in as-deposited samples irrespective of the Tb-concentration with squareness close to unity. The post-annealing results show improved PMA in FeCo-dominant films; however, the PMA reduces when Tb-content is increased.