Investigation of perpendicular magnetic anisotropy of CoFeB by x-ray magnetic circular dichroism

We have studied the variation of perpendicular magnetic anisotropy (PMA) of CoFeB layers with the oxidation degree of the MgO buffer layers. After annealing at 330 degrees C, the out-of-plane anisotropy field (H-k) of 1.5-nm CoFeB could be optimized to 3.1 kOe. To investigate the orbital hybridization of the Fe-3d and O-2p, the orbital moments per hole (m(orb)/N-h) of Fe in annealed CoFeB layers were extracted by using x-ray magnetic circular dichroism. The dependence of m(orb)/N-h on the oxidation time of MgO coincided with that of H-k, which revealed that PMA of annealed CoFeB originated from the interfacial orbital hybridization. (C) 2012 American Institute of Physics. [http://dx.doi.org/10.1063/1.4707380]