Magnetic domain reversal in ultrathin Co(001) films probed by giant magnetoresistance measurements

The magnetic domain reversal behavior in an ultrathin Co film with in-plane anisotropy that forms part of a spin-valve structure has been investigated by giant magnetoresistance and magneto-optical Kerr effect measurements. We demonstrate that minor loops can be used to obtain detailed information on the held-dependent domain process. 90 degrees domain boundaries are found to be strongly dominant over 180 degrees walls in the demagnetized state, but the magnetization reversal process is controlled by 180 degrees domain-wall motion. The 180 degrees walls are found to undergo multiple jumps mainly due to domain-wall pinning associated with interface roughness.