Magneto-optics in pure and defectiveGa1−xMnxAsfrom first principles

Abstract

The magneto-optical properties of ${\mathrm{Ga}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{As}$ including their most common defects were investigated with precise first-principles density-functional full-potential linearized augmented plane wave calculations in order to: (i) elucidate the origin of the features in the Kerr spectra in terms of the underlying electronic structure; (ii) perform an accurate comparison with experiments; and (iii) understand the role of the Mn concentration and occupied sites in shaping the spectra. In the substitutional case, our results show that most of the features have an interband origin and are only slightly affected by Drude-type contributions, even at low photon energies. While not strongly affected by the Mn concentration for the intermediately diluted range $(x\ensuremath{\sim}10%)$, the Kerr factor shows a marked minimum (up to 1.5\ifmmode^\circ\else\textdegree\fi{}) occurring at a photon energy of $\ensuremath{\sim}0.5\phantom{\rule{0.3em}{0ex}}\mathrm{eV}$. For interstitial Mn, the calculated results bear a striking resemblance to the experimental spectra, pointing to the comparison between simulated and experimental Kerr angles as a valid tool to distinguish different defects in the diluted magnetic semiconductors framework.