Selective surface/interface characterization of thin garnet films by magnetization-induced second-harmonic generation

Abstract

Magnetization-induced second-harmonic generation (SHG) has been used for the study of thin garnet films. The strong optical absorption of these films at the second harmonic frequency provides a unique possibility to study magnetic and structural properties of the film surface and film/substrate interface separately. When studied in transmission at normal incidence all relevant elements of the crystallographic part of the nonlinear optical susceptibility tensor vanish identically, while a magnetization-induced contribution remains. The purely magnetic origin of SHG from the interface is unambiguously demonstrated. From measurements of the SHG rotational anisotropy and magnetic field dependence, the surface is found to have inclusions which act as nonmagnetic sources of SHG, while the anisotropy causing easy in-plane magnetization is found to be stronger at the interface with the substrate than at the surface of the film.