Trace impurities of vanadium in Lely-grown silicon carbide single crystals have been detected by their strong, polytype-specific photoluminescence in the 1.3-1.5 mym near-infrared spectral rang, as well as by infrared absorption. A high 0/A high-, and possibly also as a deep donor. The role of vanadium as minority-carrier lifetime killer in SiC-based optoelectronic devices is suggested from these data

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Structural investigations at room temperature revealed that TbNi 2 does not crystallize in the Laves phase structure, but shows a superstructure of the Laves phase with the space group F -43m. Susceptibility, specific heat, magnetostriction and magnetoresistance measurements on polycrystalline specimens showed an additional magnetic phase transition at T R = 14 K below the Curie temperature of T C = 36 ± 0.2 K. In order to clarify the nature of this magnetic phase transition at 14 K, elastic neutron diffraction below and above T R and T C was performed. The analysis of these data showed that this transition at T R is due to the rotation of the Tb moments on three of the total of eight non-equivalent Tb sites in the rhombohedrally distorted unit cell in the magnetic ordered state. This rotation of these Tb moments is out of the [111] direction into a plane perpendicular to the space diagonal. The cause for this magnetic instability is due to an interplay of the regularly arranged vacancies in the superstructure and the crystal field level position which has been studied by inelastic neutron scattering.

Magnetic-circular-dichroism (MCD) absorption and optically detected electron-spin-resonance (ESR) data for the neutral vanadium impurity, Vhigh4plus(3dhigh1) on the alpha, beta and gamma sites in 6H-SiC are presented and supplemented by linearly polarized absorption and luminescence spectra. An analysis of the linearly polarized spectra yields crystal-field-level schemes in zero magnetic field and an intensity parameter u for Vhigh4plus on each of the three Si sites. This information is used to account for the Vhigh4plus MCD zero-phonon-line positions, signs, and relative intensities without an adjustable parameter. Evidence of Jahn-Teller effects is found in both the Vhigh4plus high2 E ground and the high2 T sub2 excited states. The MCD-ESR technique, in the present case, is site selective. The Vhigh4plus resonances associated with the beta and gamma site are virtually identical and cannot be distinguished by conventional ESR. The g factors for all three sites are satisfactorily expla ined within the framework of crystal-field theory