Laser spectroscopy and crystal field analysis of energy level structure of Tm3+ ions in SrY2O4 crystal

Site-selective laser spectroscopy study of the multi-site SrY2O4:Tm3+ crystal (0.05 at.%) show that two types of impurity centers of Tm3+ ions are predominantly formed. The Stark sublevel patterns of the 3H6, 3H5, 3F4, 3H4, 3F3, and 1G4 multiplets have been determined. Calculations of the energy level structure for Tm3+ ions at Y1 and Y2 lattice sites have been carried out in the framework of the crystal-field theory. The obtained calculation results agree with the measured energy spectra, supporting an assignment of spectra to Tm3+ ions at Y1 and Y2 lattice sites. To verify the correctness of the performed calculations, the field dependencies of the magnetization along the crystallographic a, b and c axes and the temperature dependence of the magnetization in the magnetic field applied along the c-axis of the SrY2O4:Tm3+ (0.5 at.%) crystal were measured. The set of crystal-field parameters obtained in this work made it possible to fully describe the measured magnetization dependences.