Stack structure and CoFeB composition dependence of perpendicular magnetic anisotropy employing Pt heavy metal layer

Pt is an expected heavy metal material for its large spin orbit coupling effect. However, Pt layer always display a different perpendicular magnetic anisotropy (PMA) influence tendency when it fabricated with the magnetic tunnel junction adopting material CoFeB. In this research, the properties of Pt/CoFeB/MgO (bottom structure) and MgO/CoFeB/Pt (top structure) samples with different CoFeB compositions were investigated in details. It was found that the PMA properties in the bottom structure are always stronger than that in the top structure, no matter what the CoFeB composition is. Moreover, the strong PMA was obtained in the CoFeB with large Co atomic composition. According to the element distributions state analyses via high-resolution transmission electron microscopy and the elemental chemical state analyses via X-ray photoelectron spectroscopy, the reasons are attributed to the composition- and structural-dependent Pt-Co hybridization, and the influence of Fe-O hybridization by catalytic action of heavy metal Pt at CoFeB/MgO interface. The mechanism behind the obtained PMA is significant for designing non-volatile ultra-low-power magnetic memory devices based on the different structures and CoFeB compositions.