Element-specific spin and orbital moments and perpendicular magnetic anisotropy in Ta/CoFeB/MgO structures

Perpendicular magnetic anisotropy (PMA) in the Ta/CoFeB/MgO system has been studied using x-ray magnetic circular dichroism and vibrating sample magnetometry. The ratios of the orbital to spin magnetic moments of Co atoms in the Ta/CoFeB/MgO structures with PMA have been found to be enhanced by 100%, compared with the Ta/CoFeB/Ta structure without PMA. The orbital moments of Co are as large as 0.30 μ B, more than half of their spin moments in the perpendicularly magnetized Ta/CoFeB/MgO structures. The results indicate that the PMA observed in the CoFeB/MgO structures is related to the increased spin-orbital coupling of the Co atoms. This work offers experimental evidence of the correlation between PMA and the element-specific spin and orbital moments in the Ta/CoFeB/MgO systems.