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 field-dependent domain process. 90° domain boundaries are found to be strongly dominant over 180° walls in the demagnetized state, but the magnetization reversal process is controlled by 180° domain-wall motion. The 180° walls are found to undergo multiple jumps mainly due to domain-wall pinning associated with interface roughness.

• Received 3 August 1999

DOI:https://doi.org/10.1103/PhysRevB.61.6871