Vectorial magnetometry with second-harmonic generation effect in studies of implantation induced inhomogeneity in garnet films.

The magnetization-induced second-harmonic generation (MSHG) effect was applied to study changes of magnetization distribution caused by H+2 ions implantation in magnetic garnet film of (111) symmetry. The evolution of the magnetization vector m in perpendicular magnetic field H was studied as a function of coherently rotated polarizers by an angle φ. The I2ω(H, φ) intensities exhibit completely different character as compared to the unimplanted film. The experimental results were explained in the frame of a phenomenological model of the MSHG effect, developed for the structure of 3m symmetry, composed of implanted and unimplanted sublayers. The theoretical approach allowed to determine the amplitudes and phases of nonlinear optical susceptibility tensor elements χ[2] as well as the m(H) vector components. In contrast to the linear magneto-optical Faraday effect, application of nonlinear MSHG method allows for simultaneous determination of all components of the magnetization vector in single experiment. It was found that contributions from the sublayers associated with mz components enter to the MSHG effect with opposite signs due to difference in phases of χ[2]. It is shown that m vector in the implanted sublayer undergoes spatial evolution vs H during the magnetization process, with a complex trajectory corresponding to the reorientation of the m(H) from sample plane to the normal direction. The developed methods can be useful in studies of other magnetic materials with intrinsic or artificially introduced inhomogeneities. [ABSTRACT FROM AUTHOR]