EPR observations of trivalent titanium in orthophosphate single crystals

The ground state spectroscopic properties of the 3d1 electronic configuration ion Ti3+ have been investigated using EPR spectroscopy. Trivalent titanium was incorporated as a dilute impurity in single crystals of the tetragonal, zircon-structure hosts ScPO4, YPO4, and LuPO4. The EPR spectrum of Ti3+ was observed in the as-grown orthophosphate crystals, and low temperature irradiations were not required to produce the trivalent state. The EPR results show that Ti3+ occupies a substitutional cation site in the host orthophosphate single crystals. Axial spin-Hamiltonian parameters were determined at 77 K, and these results are compared to those obtained previously for the 4d1 and 5d1 configuration ions Zr3+ and Hf 3+ in the same host crystals. Titanium-doped orthophosphate crystals containing isotopically enriched 47Ti or 49Ti were also grown and employed in determinations of the hyperfine parameters. The g-values observed here for Ti3+, and determined previously for Zr3+ and Hf 3+ are not accounted for by the published second-order expressions indicating that additional coupling mechanisms are operative.