Probing magnetic inhomogeneity in La0. 67Ca0.33MnO3 by optical spin wave resonances

We report on our recent study of spin wave resonances in ferromagnetic La0.67Ca0.33MnO3 (LCMO) thin films by ultrafast Kerr-rotation experiments. Coherent magnetization precessions were generated and detected by subpicosecond laser pulses. Confined higher order spin wave modes are identified in addition to fundamental modes at 10 K. We determine spin stiffness, magnetic and surface anisotropy parameters for both 60-nm and 100-nm LCMO samples. Significant changes in anisotropy parameters are explained by the formation and extension of magnetic inhomogeneity in the 100-nm LCMO film. Our results show the new picosecond time-resolved magneto-optical method is a powerful tool for detecting magnetic inhomogeneity.