Theoretical Investigations on the Anomaly of the g Factors and Local Structure for LaCuO3−δ

Abstract

The anomaly of the g factors and local structure for LaCuO3-delta are theoretically investigated from the perturbation formulas of the g factors for a 3d (9) ion in tetragonally distorted tetrahedra based on the cluster approach including the ligand contributions. The anomaly (g (ayen)> 2 > g (aSyen)) of the g factors is ascribed to the paramagnetic Cu2+ (originating from the host diamagnetic Cu3+ capturing one electron under oxygen deficiency) in a tetragonally elongated tetrahedron. The tetragonal distortion angle is found to be about 3.56A degrees (i.e., the Cu2+-O2- bond angle related to the C-4 axis is 3.56A degrees smaller than that (a parts per thousand 54.74A degrees) of a regular tetrahedron) due to the Jahn-Teller effect. The coordination number decreases from the original six for the host octahedral Cu3+ in LaCuO3-delta to four for the tetrahedral impurity Cu2+ in LaCuO3-delta arising from incomplete Cu2+-O2- bonding due to oxygen deficiency and some Cu2+ locating in the surface of the sample.