Perpendicular magnetic anisotropy in the CoFeB/Pt multilayers by anomalous Hall effect

The perpendicular magnetic anisotropy (PMA) in as-deposited [CoFeB/Pt](n) multilayer is studied by using anomalous Hall effect. A clear PMA is observed in the ultrathin (similar to 0.5 nm) amorphous CoFeB layer sandwiched by Pt. The PMA in as-deposited [CoFeB/Pt](n) multilayers is strongly dependent on the thicknesses of CoFeB, Pt, and the number of CoFeB/Pt bilayers. With the increase of the number of CoFeB/Pt bilayers (n >= 5), the hysteresis loop changes from rectangular to bow-tie shaped, and then the net moment approaches to zero in the remnant state. Moreover, the coercivty of [CoFeB/Pt](n) multilayers is much low, which meets the requirement for free perpendicular electrode in the future spintronic device.