Optical conductivity of MnN: a combined experimental and theoretical study.

A comparison between measured and calculated optical conductivity is presented for MnN films prepared by ion assisted deposition. X-ray diffraction and extended x-ray absorption fine structure show the films to be nanocrystalline but phase pure. X-ray emission spectroscopy of the N K-edge and X-ray absorption near edge spectroscopy of the N K- and Mn L-edges are used to probe the occupied and empty densities of states, which compare well with the N-2p and Mn-3d partial densities of states calculated using the linearized muffin-tin orbital method. The optical conductivity was measured by spectroscopic ellipsometry/reflectivity in the infared to UV range. The major differences between calculated and measured spectra can be understood on the basis of a limited electron mean-free-path in these nanocrystalline films, which relaxes the momentum conservation requirement. The calculated optical functions are analyzed in terms of their dominant band-to-band contributions including the polarization dependence. The temperature dependent conductivity shows a clear metallic behaviour and a weak Kondo-like low temperature anomaly.