Influence of the exchange interaction on far-infrared spin-flip resonances in zero-gapHg1−xMnxSe

Abstract

Far-infrared (FIR) magnetotransmission experiments were carried out on the diluted magnetic ("semimagnetic") semiconductor ${\mathrm{Hg}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Se}$ with $x=0.03$ with the use of an optically pumped FIR laser. Measurements were performed in magnetic fields up to 2.5 T in both Voigt and Faraday geometries, at FIR wavelengths between 96.5 and 170 \ensuremath{\mu}m in the temperature range between 1.9 and 6.5 K. We report the observation of the electric-dipole-excited conduction-electron-spin-resonance (EDSR) and combined-resonance transitions. These intraband spin-flip resonances are made possible by the relaxation of the electric-dipole selection rules through the $\stackrel{\ensuremath{\rightarrow}}{\mathrm{k}}\ifmmode\cdot\else\textperiodcentered\fi{}\stackrel{\ensuremath{\rightarrow}}{\mathrm{p}}$ interaction or inversion asymmetry, in the presence of spin-orbit coupling. Because of the exchange interaction between the conduction electrons and the magnetic moments localized on the ${\mathrm{Mn}}^{2+}$ ions, the spin splitting of the electronic Landau levels is extremely large and is temperature dependent. This manifests itself as a dramatic temperature variation of the positions of EDSR and of the combined resonance. The results of the experiments are analyzed with a numerical fitting procedure using the Pidgeon-Brown model which has been modified to include the effects of the exchange interaction. The analysis yields conduction band and exchange parameters for ${\mathrm{Hg}}_{1\ensuremath{-}x}{\mathrm{Mn}}_{x}\mathrm{Se}$ of small Mn content.