Two similar new dopant-related defects were identified, using electron spin resonance techniques, in V-doped and Mo-doped single crystals. The defects resembled the VO•(B) center (electron associated with an O vacancy) which had been found earlier in electron-irradiated undoped samples. The new centers were appreciably modified by a perturbing V or Mo dopant ion which replaced a W cation that neighbored the trapped electron. Spin-Hamiltonian parameters were determined. The diffuse nature of the electron wave-function was indicated by interactions with an adjacent dopant ion and an adjacent W ion. The defects were referred to as VO•(B)VW and VO•(B)MoW centers.

A.Watterich, G.J.Edwards, O.R.Gilliam, L.A.Kappers: Journal of Physics - Condensed Matter, 1996, 8[49], 10659-67