$\mathrm{MnTe}$ with a hexagonal structure of $\mathrm{NiAs}$ type is an antiferromagnetic semiconductor below the Néel temperature $T_N=310\mathrm{K}$. The spin-wave excitations of a $\mathrm{MnTe}$ single crystal have been measured at $T=11\mathrm{K}$ by inelastic neutron scattering. The experimental spin-wave dispersions, obtained along five high-symmetry directions of the reciprocal space, have been modeled with a Heisenberg Hamiltonian including isotropic exchanges up to the third nearest neighbors and a planar magnetic anisotropy. This yielded the exchange integral values $J_1=-21.5\mathrm{K}$, $J_2=0.67\mathrm{K}$, and $J_3=-2.87\mathrm{K}$. These results are presented and compared to experimental values of relevant diluted magnetic semiconductors, allowing a discussion on a generic description of the distance dependence of the nearest-neighbor magnetic interactions.

Spin-wave excitations of a MBE-grown single crystal of MnTe with a zinc-blende structure have been measured by inelastic neutron scattering in the type-III antiferromagnetic low-temperature phase of this compound. The experimental data have been modeled with a Heisenberg Hamiltonian including isotropic exchanges and magnetic anisotropy. Exchange constants and anisotropy terms have been estimated, which allowed a discussion on the relative importance of distant neighbors. The relevance of anisotropic exchanges is also discussed. The assumption of a collinear spin arrangement provides a consistent description of the spin-wave spectrum, including inelastic-neutron-scattering cross section. The temperature dependence of the spin waves revealed an anomalously strong damping, which starts well below the transition temperature.

With micro-Raman spectroscopy and x-ray diffraction (XRD), we studied ZnO crystals implanted with Mn, Fe, Co, and Ni, respectively, with implantation concentrations from 4 up to $16\text{at}\text{.}\%$ . Using thermal treatments in air up to $700°\text{C}$ , we analyzed the annealing effect on the ZnO crystal lattice as well as the onset of secondary phases and their microstructure on the sample surface. While the $500°\text{C}$ treatment induces a considerable annealing, secondary phases are observed for transition metal (TM) concentrations $\ge 8\text{at}\text{.}\%$ after the treatment at $700°\text{C}$ . Their microstructure strongly depends on the TM species. Various stoichiometric and nonstoichiometric TM oxide precipitates as well as elemental TM clusters are identified by their Raman and XRD signatures and their possible magnetic impact is discussed.

Results on the absorption of intracenter transitions of the ${\mathrm{Cr}}^{2+}$ impurity charge state ($3d^4$) in GaAs are reported for different samples with various free carrier and chromium concentrations. The analysis of the data gives limiting values for the Jahn-Teller energies in the ground and excited states of the ${\mathrm{Cr}}^{2+}$ impurity. The strengths of these couplings are discussed with different models. The effect of the hydrostatic pressure up to 10 kbars at 300 and 77 K is also reported and it is shown that, in specific conditions, the ${\mathrm{Cr}}^{1+}\left(3\mathrm{}{d}^5\right)$ state can be activated by the pressure against the ${\mathrm{Cr}}^{2+}$ state. These experiments prove that the ${\mathrm{Cr}}^{1+}$ energy level is above the GaAs conduction band.