THEORY OF NONLINEAR MAGNETOOPTICAL IMAGING OF MAGNETIC DOMAINS AND DOMAIN-WALLS

A symmetry analysis of nonlinear magneto-optical imaging of magnetic d omains and domain walls is presented. We introduce gradient terms givi ng rise to the magnetization-induced second-harmonic generation (MSHG) via spatial derivatives of the magnetization. The nonvanishing indepe ndent elements of the relevant tensors are derived for cubic media. Di fferent contributions to the MSHG image from domains and domain walls are analyzed for thin magnetic films with different symmetry. it is sh own that measurements of polarization properties of the MSHG response may yield information about the relative importance of different magne tization-induced contributions and also the type of domain walls.