Magnetization reversal in CoFe/Ag/Fe/ZnSe thin layer sandwiches

In recent work [J. Appl. Phys. 70, 10 (1991)] the spin valve effect (SVE) was measured in Co_xFe_1-x/Ag/Fe(x<0.7) thin layer sandwiches grown by molecular beam epitaxy. The field dependence of the SVE was correlated with VSM magnetization data taken on the samples. It was found that only at low fields was there a correlation between the SVE resistance and the magnetization data. These results indicated a more complex reversal mechanism that included substantial magnetizations in directions not measured in traditional VSM measurements. In order to more accurately determine the field-dependent magnetization of the samples during reversal, the longitudinal and transverse Kerr effects were measured on the layers. The particular geometry used to measure the Kerr effects was for the light scattering plane to be perpendicular to the applied magnetic field. The transverse Kerr effect data, which in this geometry are sensitive to the magnetization parallel to the applied magnetic field, replicated the VSM data. The longitudinal Kerr effect, which is sensitive to the net magnetization perpendicular to the applied field (in the plane of the film), indicated a substantial perpendicular magnetization component. Based upon previous work on epitaxial iron films, it appears that the magnetization reversal process proceeds by transitions between easy axes. From these measurements, the anomalous resistances observed as a function of the applied magnetic field in J. Appl. Phys. 70, 10 (1991), are explained by having one of the films soft, and two easy axes in the plane of the other film.