Direct imaging of spin-reorientation transitions in ultrathin Ni films by spin-polarized low-energy electron microscopy

The thickness-dependent spin-reorientation transition (SRT) in ultrathin Ni films grown on a stepped Cu(100) substrate was studied by spin-polarized low-energy electron microscopy (SPLEEM). Magnetic contrast in SPLEEM is proportional to the scalar product of beam polarization and magnetization of the film. This dependence was exploited to determine the local 3D magnetization vector by evaluating magnetic contrast in images obtained using three orthogonal polarizations of the incident electron beam. Using this method, we were able to directly image the rotation of the magnetization vector in Ni films from in-plane and parallel to the steps to out-of-plane and perpendicular to the steps of the substrate. We found the SRT to proceed via two mechanisms: continuous growth of the out-of-plane component, accompanied by discontinuous reorientation of the in-plane component via domain nucleation. Published in 2006 by John Wiley & Sons, Ltd.