Nonlinear magneto-optical spectroscopy of YCrO_3 and GaFeO_3

摘要

Second harmonic generation (SHG) was observed from yttrium orthochromite (YCrO_3) crystals with centrosymmetric structure. The origin of the SHG was determined to be a magnetic-dipole transition considering the resonant structure of SHG spectra and its polarization dependence. The intensity of SHG shows the drastic change at the Neel temperature under magnetic field and this fact suggests the effects from magnetic ordering. Along with the spectrum of the SHG intensity, phase of the nonlinear susceptibility was measured by analyzing the polarization characteristics of superposed fields from the sample and reference. The result shows that axial i-type χ~((2)) value is pure imaginary at the peak wavelength. Gallium ferrite (GaFeO_3) has simultaneously four types of nonlinear optical tensors including polar i-, axial i-, polar c- and axial c-types. We observed SHG originating from c-type components by employing the experimental configuration where each contribution is separable. Structures of spectra and their relation to magnetic properties are discussed.