Fine-structure anomalies in EPR spectra of Gd3+ centres formed in TlCdF3 single crystals

Electron paramagnetic resonance (EPR) measurements have been made on as-grown single crystals of perovskite-type TlCdF3 at room temperature in the cubic phase. Signals from two kinds of tetragonal Gd3+ centre are observed. One centre observed in the Gd-only-doped crystal is ascribed to a Gd3+ ion at a Cd2+ site being associated with a vacancy at the nearest Cd2+ site. The other centre observed in the Gd, Li co-doped crystal is ascribed to a Gd3+ ion at a Cd2+ site being associated with a Li+ ion at the nearest Cd2+ site. The fine-structure terms are discussed by separating them into the uniaxial and cubic terms. Anomalous values of the axial and cubic parameters are obtained for TlCdF3 in contrast with the parameters for other host crystals ACdF3 (A = K, Rb, Cs)