Calculated magneto-optical properties of pure and doped MnBi

Abstract

The magneto-optical properties of MnBi show some striking features which we address here by calculating the Kerr spectra of pure MnBi, as well as of (X = Mn, Si, Al, O and Pt) and (X, Y) = (Al, Al) and (Al, O), (Pt, Pt). This system of compounds constitutes an example for which we demonstrate how much first-principles calculations can achieve and how our findings can be used to advance our knowledge of the origin of magneto-optical properties. Our calculations are based on the local density functional approximation (LDA) and the augmented spherical wave (ASW) band structure method including the scalar - relativistic and spin - orbit coupling terms to determine the effective one-electron energies and wavefunctions. From this we derive the inter-band and intra-band contributions to the optical conductivity tensor. Our results allow some statements concerning the connection of material properties with the magneto-optical properties. Thus, for instance, we are led to believe that oxygen plays an important role in explaining the experimental Kerr spectrum of pure MnBi. Furthermore, the measured enhancement of the Kerr angle in Al-alloyed MnBi is most probably not due to the occupation of interstitial sites by Al atoms. In contrast to this is Pt-alloyed MnBi, for which our calculations indicate that Pt partly occupies interstitial sites.