Dielectric tensor for magneto-optic NiMnSb

Abstract

The diagonal component « xx and off-diagonal component « xy of the complex dielectric tensor for the ferromagnetic compound NiMnSb are determined using ex situ spectroscopic ellipsometry and magneto-optic analysis over the spectral range from 0.7 to 6.2 eV. The effects of the overcoat on the raw data are removed by the analysis. First, the complex « xx of thin-film NiMnSb were determined byex situ spectroscopic ellipsometry; then « xy was determined by analyzing Kerr rotation and ellipticity data using the determined « xy data. Lorentz oscillators were used to model peaks seen in the « xx spectra. The diagonal dielectric component « xx is dominated by free-carrier effects below 1.15 eV, and dominated by interband transitions above 2.0 eV. The center energies of the Lorentz oscillators are consistent with the calculated band structure and minority-spin optical conductivity of NiMnSb. Joint density of states and optical conductivity calculated from « xx(2) data with free-carrier effects removed shows onset energies at ;0.6 and ;0.2 eV, respectively. From a study of the « xx and « xy spectra, the Kerr rotation peak at lower energy is determined to be due to combined contributions from: ~1! a crossover between the free-carrier effect and interband transitions, and ~2! transitions involving spin-orbit coupling. The high-Kerr rotation peaks at higher energies result exclusively from transitions involving spin-orbit coupling. @S0163-1829~99!13615-4#