The magneto-optic (MO) Kerr and Faraday spectra for manganese pnictides are calculated using the all electron, relativistic, full-potential linear muffin-tin orbital method. The amplitude of our calculated spectra are found to be in good agreement with corresponding experimental spectra. Although the MO property is a rather complicated function of the diagonal and off-diagonal elements of the optical conductivity tensor, present theory nevertheless provides very practical insight about its origin in these compounds. The largest Kerr effect observed in MnBi can be understood as a combined effect of maximal exchange splitting of Mn $3d$ states and the nearly maximal spin-orbit (s-o) coupling of Bi. The frequency-dependent optical properties, namely reflectivity, absorption coefficient, electron-energy-loss spectra, refractive index, extinction coefficient are given. From our calculations (including spin-orbit coupling and orbital polarization) the site-projected spin and orbital moments are also obtained and compared to the available experimental values and a good agreement is found. The magnetic anisotropy energy is calculated with a minimal number of approximations for the three systems. A disagreement between theory and experiment is found. Using the generalized gradient corrected full-potential linear augmented plane-wave method we have calculated the unscreened plasma frequencies and the hyperfine parameters such as electric-field gradient as well as the hyperfine field.

• Received 21 August 1998

DOI:https://doi.org/10.1103/PhysRevB.59.15680