Collapse of hard-axis behavior in uniaxial Co films

We study the magnetic properties of weakly disordered Co films with in-plane uniaxial magnetocrystalline anisotropy. The growth sequence used allowed the controlled introduction of grain orientation disorder. Above a threshold disorder level, we observe an anomalous magnetic reversal near the nominal hard axis; while the behavior in all other field orientations is barely affected. A two-grain model explains the anomaly as the occurrence of nonuniform magnetization states near the hard axis, a fact that is experimentally confirmed by Kerr microscopy.