PARAMAGNETIC DEFECTS IN ZNWO4 SINGLE-CRYSTALS INDUCED BY ELECTRON-IRRADIATION AT ROOM-TEMPERATURE

Intrinsic paramagnetic defects in undoped zinc tungstate single crysta ls have been observed by ESR after electron irradiation at room temper ature. The only observed hole-type defect is attributed to a hole trap ped at an O2- ion near a zinc vacancy. Two electron-excess centers are each due to a single electron trapped at an oxygen vacancy, where the defects differ in the oxygen vacancy positions. All of the defects ex hibit superhyperfine interactions with neighboring W-183 nuclei. Spin- Hamiltonian parameters are reported and discussed.