Theoretical studies of the g factors for the tetragonal Cu2+ site in Y2BaCuO8

•EPR g factors are theoretically studied for tetragonal Cu2+ site in Y2BaCuO8.•Low symmetrical distortion is quantitatively involved from superposition model.•Oxygen octahedron shows relative elongation 2% along c axis due to Jahn-Teller effect. The EPR g factors g// and g⊥ for the tetragonal Cu2+ site in Y2BaCuO8 are theoretically studied from the perturbation formulas of the g factors for a 3d9 ion in a tetragonally elongated octahedron. In the calculations, the influences of the covalency and the low symmetrical (tetragonal) distortion are included, and the tetragonal field parameters are obtained using the superposition model. The [CuO6]10− cluster is found to experience the relative axial elongation of about 2% along the crystalline c axis due to the Jahn–Teller effect. The calculated g factors show good agreement with the experimental data. The relationship between the g anisotropy g//–g⊥ and the tetragonal distortion is discussed.