An EPR Study of Divacancy Centres in CaWO4

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Abstract
Two paramagnetic defects with spin S = 1/2 have been identified in CaWO4 after neutron irradiation. The EPR spectra of these defects fit the spin‐Hamiltonian ℋ = β S g̃ B + SÃ (I1 + I2) with g1 = 1.811, g2 = 1.785, g3 = 1.497 and g1 = 1.766, g2 = 1.774, g3 = 1.429. The hyperfine structures for both centres are identical, arising from the 14% abundant 183W isotope at two equivalent sites. The hyperfine tensors have components A‖ = 167.4 × 10−4 cm−1 and A⊥ = 87.4 × 10−4 cm−1 with I1 = ±1/2 or 0 and I2 = ±1/2 or 0. The detailed analysis of the spectra, magnitude of the spin‐Hamiltonian parameters and tensor axes are consistent with the two spectra arising from different charge states of oxygen divacancy centres located on adjacent WO complexes.