Interband magnetoabsorption in semimagnetic semiconductor alloysHg1−kMnkTewith a positive energy gap

Low-temperature infrared magnetoabsorption experiments were carried out on ${\mathrm{Hg}}_{1-k}{\mathrm{Mn}}_k\mathrm{Te}$ mixed crystals with compositions corresponding to the semiconducting (positive energy gap) range. Measurements were performed in the spectral region 100-350 meV in Voigt and Faraday geometries, using both linear and circular polarizations. The magneto-optical data provide observation of interband ${\Gamma }_8\to {\Gamma }_6$ transitions. In addition, transitions from acceptor levels to ${\Gamma }_6$ Landau levels were observed. The interband magneto-optical transitions are interpreted within the framework of the Pidgeon-Brown model, modified by the contributions of the $s-d$ and $p-d$ spin-spin exchange interaction between band electrons and localized ${\mathrm{Mn}}^{2+}$ spins. From the theoretical fits of the transition energies to the observed absorption lines, the relative magnetization $A(H,T)\mathrm{}$ is deduced at $T=4.2\mathrm{} \mathrm{and} 2$ K for alloys of various Mn content. In contrast with zero-gap ${\mathrm{Hg}}_{1-k}{\mathrm{Mn}}_k\mathrm{Te}$, in the present case $A(H,T)\mathrm{}$ exhibits a nearly linear magnetic field dependence and depends only weakly on temperature. These features are related to the strong antiferromagnetic interactions between the localized magnetic moments. Conduction electrons in crystals in this composition range exhibit large and positive $g$ factors as a consequence of the $s-d$ exchange coupling.