Studies on the EPR g factors for the oxygenated and nonoxygenated BaCuO2+x.

The EPR g factors for the oxygenated and nonoxygenated BaCuO 2+ x are theoretically studied from the perturbation formulas of the g factors for an orthorhombically elongated octahedral 3d 9 complex based on the cluster approach. The relative axial elongation ratios (≈1% and 0.6%) along c axis and the relative planar bond length variations (≈6.9% and 8.9%) are found for the oxygenated and nonoxygenated systems, respectively. The above local orthorhombic distortions of the Jahn–Teller nature around Cu 2+ can suitably account for the axial and perpendicular anisotropies of the observed g factors. The present studies can be useful to understand the influences of this parasitic phase BaCuO 2+ x on the EPR behaviours and superconductivity of the R 123 high T c superconductors. [ABSTRACT FROM AUTHOR]