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

Magnetoabsorption associated with ${\Gamma }_6\to {\Gamma }_8$ transitions was investigated at 4.4 °K, on pure $n$-type HgTe thin crystals in the spectral region 300-400 meV for $\sigma$ and $\pi$ polarizations. Analysis of experimental spectra is performed using both the three-band model (including the nonparabolicity), and the theory of Luttinger. Band parameters are determined by fitting transition energies: $E_{{\Gamma }_8}-E_{{\Gamma }_6}=302.5\mathrm{}$ meV, $\frac{m_{{\Gamma }_6}}{m_0}=0.028\mathrm{}\pm 0.001$, and $g_{{\Gamma }_6}=-41\mathrm{}\pm 4$ at $\Gamma$. ${\Gamma }_8$ Luttinger parameters (${\gamma }_1=-12.8,\overline{\gamma }=-8.4,\kappa =-10.5\mathrm{}$) satisfactorily explain interband and intraband ${\Gamma }_8$ magnetoabsorption. The structure of ${\Gamma }_8$ magnetic levels near $\Gamma$ is quantitatively described by calculating the $k_H$ dependence of the energies in the [111] direction. A complex structure is found for a set of heavy holes.

Accurate measurements of the imaginary part of the complex susceptibility are used in order to compare the validity of different dynamic scaling models on the two related spin-glass compounds ${\mathrm{Hg}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$Te and ${\mathrm{Cd}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Mn}}_{\mathrm{x}}$Te (x=0.3). The conventional power-law scaling yields in both compounds a dynamic exponent zν=9±1, $T_c$=8.4 K for ${\mathrm{Hg}}_{0.7}$ ${\mathrm{Mn}}_{0.3}$Te and 6.45 K for ${\mathrm{Cd}}_{0.7}$ ${\mathrm{Mn}}_{0.3}$Te. The generalized in-field scaling leads to an independent and consistent determination of $T_c$. Good scalings may also be achieved according to activated dynamics, but the P values appear to differ in various systems, a result at odds with the expected universality of the critical exponents.