THEORY FOR THE NONLINEAR MAGNETOOPTICAL KERR-EFFECT AT FERROMAGNETIC TRANSITION-METAL SURFACES

We present a theory for determining the linear and nonlinear magneto-optical Kerr spectra of Fe, in particular the nonlinear Kerr angle. We derive and discuss general features of the linear and nonlinear Kerr effects, especially the details of their dependence on exchange interaction and magnetization (Fermi-level crossings), frequency, and spin-orbit interaction. Furthermore, we demonstrate how various electronic material properties, such as d-band width, s-d hybridization or band narrowing due to electronic correlations or caused by geometry (reduced coordination number in thin films), can be extracted from the spectra. Also we present results for the nonlinear Kerr angle. Most interestingly, we find that the nonlinear Kerr angle might be larger than the linear one.