The Optical Properties of MnAs and MnAs 0.85 P 0.15

The reflectivity spectra of MnAs (hexagonal NiAs structure) and MnAs 0.85 P 0.15 (orthorhombic lattice) are measured in the energy range 0.3 to 14 eV at room temperature and a Kramers‐Kronig analysis is performed. It is found that below 1 eV plasma effects due to free d‐electrons dominate. At energies from 3 to 8 eV plasma resonances due to bound d‐electrons are observed. In the intermediate region, the imaginary part of the dielectric constant ϵ 2 reveals structure due to transitions between d‐states and from the valence band into d‐ and sp states. Analysis of the combined density‐of‐states function ϵ 2 E 2 yields 3.0 eV for the energy gap between bonding and antibonding sp states for both compounds. Also, from interpretation of ϵ 2 together with ϵ 2 E 2 the energy separation between the Fermi level E F and the bottom of the minority spin e‐band and the distance of the valence band edge from E F are obtained.