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 use Kerr microscopy alongside electrical transport measurement to gain insight into the underlying switching mechanisms of 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 the edge of the device which modelling reveals is likely assisted by the perpendicular component of the Oersted field. Further domain growth, leading to magnetisation reversal may be assisted by spin torques.