Theoretical studies on the EPR g factors for Dy3+ in YBa2Cu3O6

In the past years, the typical high Tc superconductor YBa2Cu3O6 has been extensively studied by many authors. And electron paramagnetic resonance (EPR) studies of rare-earth (Re 31) ions in high-Tc oxide superconductors have attracted much interest because they can provide valuable information on spin-lattice relaxation, exchange interactions and the ground state properties of Re 31 ions, which are further employed as sensitive probes of spin dynamics in high-Tc superconductor. The EPR anisotropic g factors of Dy3+ in YBa2Cu3O6 crystal has been measured by M.R. Gafurov et al., and there is no theoretical explanations related to the crystal structural data. In this paper, parameters g factors for Dy3+ in YBa2Cu3O6 are theoretically studied from the perturbation formulas of these parameters for a 4f(9) ion in tetragonal symmetry. In these formulas, the contributions to the EPR parameters from the second-order perturbation terms and the admixtures of various excited states are taken into account. The related crystal-field parameters are determined from the superposition model and crystal structural data. The theoretical results show reasonable agreement with the experimental values.