MnTe with a hexagonal structure of NiAs type is an antiferromagnetic semiconductor below the Néel temperature T N = 310 K. The spin-wave excitations of a MnTe single crystal have been measured at T =11 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 K, J 2 = 0.67 K, and J 3 = −2.87 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.

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Mn-doped GaAs nanowires were grown in the self-catalytic growth mode on the oxidized Si(100) surface by molecular beam epitaxy and characterized by scanning and transmission electron microscopy, Raman scattering, photoluminescence, cathodoluminescence, and electron transport measurements. The transmission electron microscopy studies evidenced the substantial accumulation of Mn inside the catalyzing Ga droplets on the top of the nanowires. Optical and transport measurements revealed that the limit of the Mn content for self-catalysed growth of GaAs nanowires corresponds to the doping level, i.e., it is much lower than the Mn/Ga flux ratio (about 3%) used during the MBE growth. The resistivity measurements of individual nanowires confirmed that they are conductive, in accordance with the photoluminescence measurements which showed the presence of Mn(2+) acceptors located at Ga sites of the GaAs host lattice of the nanowires. An anomalous temperature dependence of the photoluminescence related to excitons was demonstrated for Mn-doped GaAs nanowires.

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 at. %. Using thermal treatments in air up to 700 °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 °C treatment induces a considerable annealing, secondary phases are observed for transition metal (TM) concentrations ≥8 at. % after the treatment at 700 °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.

It is shown that the growth of II-VI diluted magnetic semiconductor nanowires is possible by the catalytically enhanced molecular beam epitaxy (MBE). Zn(1-x)MnxTe NWs with manganese content up to x=0.60 were produced by this method. X-ray diffraction, Raman spectroscopy, and temperature dependent photoluminescence measurements confirm the incorporation of Mn(2+) ions in the cation substitutional sites of the ZnTe matrix of the NWs.

We review our results on the growth of ZnTe-and CdTe-based nanowires (NWs) and on their basic structural and optical properties. The nanowires were produced by using molecular beam epitaxy (MBE) with the use of a mechanism of catalytically-enhanced growth. The growth of ZnTe, CdTe, ZnMgTe and ZnMnTe nanowires was performed from elemental Zn, Cd, Mn, Mg and Te sources on the surfaces of (001)-, (110)-and (111)B-oriented GaAs substrates with Au nanocatalysts. The morphological and structural properties of the nanowires were assessed by using X-ray diffractometry, field-emission scanning electron microscopy, and high resolution transmission electron microscopy. Additional studies of the compositions of both the nanowires and the Au-rich nanocatalysts were performed with the use of energy dispersive X-ray spectroscopy. The optical properties of the NWs were assessed by using photoluminescence and Raman-scattering studies performed in both macro and micro modes. The studies revealed that binary and quaternary nanowires with average diameters from 30 to 70 nm and lengths from 1 to 2.6 µm were monocrystalline in their upper parts, their growth axis was 111 , and they grow along the [111] direction of the substrate, independent of the substrate orientation used. A Au-rich (with 20 % Ga) spherical nanocatalyst was always visible at the tip of a nanowire, thus indicating that a vapor-liquid-solid mechanism was responsible for the growth of the ZnTe-and the CdTe-based nanowires. The formation of homogeneous mixed crystal ZnMnTe and ZnMgTe nanowires was demonstrated by measurements of the variation of the lattice constant and by Raman experiments that revealed the expected shift and appearance of new phonon lines and a strong enhancement of the LO-phonon structures for an excitation close to the exciton energy of the NW materials. The photoluminescence from the internal Mn 2+ transition between crystal-field-split energy levels ( 4 T1 → 6 A1) was observed in the ZnMnTe nanowires.

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