Magneto-optical study of anomalous magnetization reversal in the presence of anisotropy dispersion in CoPd thin films

摘要

Magnetization reversal is investigated in the presence of anisotropy dispersion in weakly disordered CoxPd100-x(x = 23, 36, 43) thin films. A fourfold in-plane magnetic anisotropy is observed for x = 23, whereas an increase of the Co:Pd ratio induces a uniaxial anisotropy in x = 36 and 43 films. Anomalous magnetization reversal appears along the hard axes (referred to as collapse of hard axes) in x = 23 and 36 films, but disappears for x = 43. The results are consistent with the two-grain Stoner-Wohlfarth model. It is argued that the collapse of the hard axes can be controlled by intergranular exchange interaction. Quadratic magneto-optical Kerr effect (QMOKE) is also observed in the films and is found to weaken if the in-plane anisotropy is lowered through the Co:Pd ratio. QMOKE is observed for magnetic field orientations near the hard axes but not exactly along it, in agreement with the two-grain Stoner-Wohlfarth model.