Four V-related electron paramagnetic resonance spectra were obtained from Bridgman material that was doped with V. Two of them were attributed to the charge states, VZn3+(A+) and VZn2+(A0), of the isolated V impurity. In the case of the ionized donor, VZn3+(A+), the spectrum revealed the typical behavior of the expected 3A2(F) ground state in tetrahedral symmetry. Incorporation at a cation lattice site could be proved by a resolved superhyperfine interaction with four Te ions. The second spectrum exhibited triclinic symmetry, and S = 3/2 was attributed to the neutral donor state, VZn2+(A0). The triclinic distortion of the cubic (Td) crystal field was suggested to be a static Jahn-Teller effect. The other 2 additional electron paramagnetic resonance spectra were attributed to nearest-neighbor V-related defect pairs. The spectrum of one of these, VZn2+-YTe, exhibited trigonal symmetry and was explained in terms of the S = 3/2 manifold of an orbital singlet ground state. An associated defect, YTe, was suggested to be responsible for a trigonal distortion of the tetrahedral crystal field of VZn2+. The spectrum of the second pair defect also exhibited trigonal symmetry, and could be described by S = 1/2. The ground-state manifold implied that a VZn3+-XTe pair was the most probable source of this spectrum. The S = 1/2 ground state was attributed to a predominant isotropic exchange interaction that coupled the S = 1 ground-state manifold of VZn3+ to an assumed S = 1/2 ground state of XTe in an antiferromagnetic orientation. The nature of the associated defects, YTe and XTe, remained unknown for both pairs since no hyperfine structure was observed; but it was thought probable that acceptor-like defects were involved.

J.Kreissl, K.Irmscher, P.Peka, M.U.Lehr, H.J.Schulz, U.W.Pohl: Physical Review B, 1996, 53[4], 1917-26