Theoretical Investigation of the EPR g-factors for Yb3+ in YBa2Cu3O7-δ

Abstract

The EPR g factors g‖, g⊥ for Yb3+ in YBa2Cu3O7−δ are studied with perturbation formulas based on the cluster approach of the spin-Hamiltonian parameters for a 4f13 ion in tetragonal symmetry. In these formulas, the contributions to the EPR parameters of the covalency effects, the admixture between the J = 7/2 and J = 5/2 states and the second-order perturbation terms are all included. The used crystal-field parameters are calculated with the superposition model and the local structural data of Yb3+ in YBa2Cu3O7−δ . The resulting EPR g factors for Yb3+ ions in the superconductor YBa2Cu3O7−δ agree reasonably with the experimental values. The results are discussed.