Studies on the Gyromagnetic Factors of the Tetragonal NdBa2Cu3O6.1

Abstract

The electron paramagnetic resonance (EPR) g factors g and g ⊥ of the tetragonal NdBa 2 Cu 3 O 6.1 are theoretically studied using the perturbation formulas of the g factors for a 4f 3 ion in tetragonal symmetry. In the calculations, the influences of the admixtures of various energy levels are considered, while the tetragonal field parameters are determined from the local structural data of Nd 3+ site using the superposition model. The theoretical g factors are in reasonable agreement with the observed values. The positive anisotropy g ⊥ − g is attributable to the elongation of the oxygen cube around Nd 3+ along the C 4 axis in NdBa 2 Cu 3 O 6.1 . The magnitude (average) of the g factors for NdBa 2 Cu 3 O 6.1 is lower than that for the previously observed NdBa 2 Cu 3 O 7−δ (0 < δ < 1). This can be ascribed to the different oxygen amount and the dissimilar local environments around Nd 3+ under different preparation conditions and parameters. Further, the lowest Kramers doublet of the present NdBa 2 Cu 3 O 6.1 is the unresolved Γ 7,8 , while that of NdBa 2 Cu 3 O 7 is Γ 6 .