LATERAL MAGNETIC INHOMOGENEITIES IN CO-CR LAYERS DETECTED BY FMR

Co-Cr layers deposited on Ge underlayers are investigated with ferromagnetic resonance (FMR). The thickness of the Co-Cr layers and the substrate temperature (Ts) during deposition were varied. Measurements with a vibrating sample magnetometer showed that an increase of Ts results in an increase of both the bulk saturation magnetisation Ms and the perpendicular coercivity Hc⊥ The FMR spectra, obtained with the applied field perpendicular to the sample, showed two resonances for all layers. The effective anisotropy field is positive for both resonances. The difference in effective anisotropy field does not change with thickness of the layer, but increases with increasing Ts. From this it is clear that the two resonances are not due to magnetic inhomogeneities in the growth direction, but must be due to lateral magnetic inhomogeneities. The influence of stress was investigated by dissolving the substrate. This did not influence the difference in resonance fields, so the lateral inhomogeneity is not caused by differences in internal stress. Inhomogeneities in composition, resulting in different values of Ms, or in geometrical structure, resulting in different values of the demagnetising factor Nd, are the most probable causes of the observed effects. The difference in NdMs for these different regions in the layer increases from 20 to 110 kA/m with increasing coercivity of the Co-Cr layer. © 1990 IEEE