Scanning Kerr microscopy study of current-induced switching in Ta/CoFeB/MgO films with perpendicular magnetic anisotropy

Ta/CoFeB/MgO trilayers with perpendicular magnetic anisotropy are expected to play a key role in the next generation of current and electric field switched memory and logic devices. In this study, we combine scanning Kerr microscopy with electrical transport measurements to gain insight into the underlying mechanisms of current-induced switching within such devices. We find switching to be a stochastic, domain-wall-driven process, the speed of which is strongly dependent on the switching current. Kerr imaging shows domain nucleation at one edge of the device, which modeling reveals is likely assisted by the out-of-plane component of the Oersted field. Further domain growth, leading to magnetization reversal, may still be dominated by spin torques, but the Oersted field provides an additional mechanism with which to control the switching process.