Boron-induced magneto-optical Kerr spectra and dielectric tensors in ferrimagnetic antiperovskite thin films

Boron-induced electronic states of antiperovskite nitrides such as ferrimagnetic Mn
4
N were investigated via a combination of polar magneto-optical Kerr effect (p-MOKE) spectroscopy and spectroscopic ellipsometry (SE). The boron content in the Mn
4
N film varied from 0 to 4.3 at.%, for which the crystal structure was maintained. The amplitude of p-MOKE spectra and the diagonal and off-diagonal dielectric tensors decreased with increasing boron content, which is in agreement with magnetic properties such as magnetic anisotropy and saturation magnetization. These results were related to the lattice expansion and displacement of the charge density in Mn
4
N by boron doping. However, the peak energy of Lorentz oscillator in the diagonal elements of dielectric tensors suggests that a dominant inter-band transition was independent of boron content.