Investigations on the Optical Spectra and EPR Parameters for Tetragonal Sm3+ Center in SmBa2Cu3O7−δ

It is of interest to study the optical spectra and EPR parameter of the rare-earth ion in the typical high Tc superconductors. The proper interpretation for these values is helpful to understand the optical and magnetic characteristics of the superconductors. In this paper, we calculate the optical spectra and EPR parameters (g factors g∥,g⊥ and hyperfine structure constants A∥, A⊥) of tetragonal Sm3+ center in YBa2Cu3O7−δ from the perturbation formulas of EPR parameters for 4f5 ion in tetragonal symmetry. In these formulas, the crystal-field J-mixing of the first and second excited-state multiplets 6H7/2 and 6H9/2 into the ground state, 6H5/2, the mixtures among the states with the same J value via spin-orbit coupling interaction and the interactions between the ground Kramers doublet Γγ and the same irreducible representation as Γγ in other 11 Kramers doublets Γx within 6HJ (J=5/2, 7/2, 9/2) states via crystal field and orbital angular momentum (or hyperfine structure) are considered. The calculated results are in reasonable agreement with the observed values. The results are discussed.