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Abstract:
Four V-related electron-paramagnetic-resonance (EPR) spectra are observed in Bridgman-grown ZnTe doped with vanadium. Two of them are attributed to the charge states VZn3+(A+) and VZn2+(A0) of the isolated V impurity. For the ionized donor, VZn3+(A+), the spectrum reveals the typical behavior of the expected 3A2(F) ground state in tetrahedral symmetry. The incorporation on a cation lattice site could be proved by the resolved superhyperfine interaction with four Te ions. The second spectrum showing triclinic symmetry and S=3/2 is interpreted as the neutral donor state VZn2+(A0). The origin of the triclinic distortion of the cubic (Td) crystal field could be a static Jahn-Teller effect. The two additionally observed EPR spectra are attributed to nearest-neighbor V-related defect pairs. The spectrum of the first one, V2+Zn-YTe, shows trigonal symmetry and can be explained by the S=3/2 manifold of an orbital singlet ground state. An associated defect "YTe" is responsible for the trigonal distortion of the tetrahedral crystal field of V2+Zn. The spectrum of the second pair defect also shows trigonal symmetry and can be described by S=1/2. The ground-state manifold implies a VZn3+−XTe pair as the most probable origin of this spectrum. The S=1/2 ground state is produced by a dominating isotropic exchange interaction coupling the S=1 ground-state manifold of V3+Zn to an assumed S=1/2 ground state of "XTe" in antiferromagnetic orientation. The nature of the associated defects "YTe" and "XTe" remains unknown for both pairs since no hyperfine structure has been observed, but most probably acceptorlike defects are involved.
