Effect of exchange on interband magneto-absorption in zero gap Hg 1-kMnkTe mixed crystals

Abstract

Magnetoabsorption experiments have been performed at 4.2 and 2 K in the spectral region 220-370 meV, on zero gap Hg1-kMn kTe alloys. The temperature and the composition dependence of the Γ6 → Γ 8 spectrum provides evidence of striking modifications in the Γ 8 and Γ6 spin sublevels due to exchange interactions between localized d electrons and mobile carriers. The theoretical interpretation of the magnetooptical spectra of alloys of low Mn composition is carried out, using the virtual crystal and the molecular field approximations, by including the s-d and p-d exchange interactions within the framework of the Pidgeon and Brown model. By a fitting procedure of the Γ6 → Γ8 transitions energies, the magnetization is determined at 4.2 and 2 K as a function of the magnetic field and the exchange parameters for the Γ 6 and Γ8 levels are evaluated. The Landau level energy spectrum established, at kH = 0, for alloys of composition up to 1.5 % exhibits a SM → SC transition induced by the magnetic field