Perpendicular magnetic anisotropy and magnetization process in CoFeB/Pd multilayer films

Abstract

Perpendicular magnetic anisotropy (PMA) and dynamic magnetization reversal process in [CoFeB $t$ nm/Pd 1.0 nm]$_n$ ($t$ = 0.4, 0.6, 0.8, 1.0, and 1.2 nm; $n$ = 2 - 20) multilayer films have been studied by means of magnetic hysteresis and Kerr effect measurements. Strong and controllable PMA with an effective uniaxial anisotropy up to 7.7$\times$ 10$^6$ J.m$^{-3}$ and a saturation magnetization as low as 200 emu/cc are achieved. Surface/interfacial anisotropy of CoFeB/Pd interfaces, the main contribution to the PMA, is separated from the effective uniaxial anisotropy of the films, and appears to increase with the number of the CoFeB/Pd bilayers. Observation of the magnetic domains during a magnetization reversal process using polar magneto-optical Kerr microscopy shows the detailed behavior of nucleation and displacement of the domain walls.