Investigations on the defect structure and the EPR parameters for AgBr:Ir²⁺

¹ Department of Applied Physics, University of Electronic Science and Technology of China, Chengdu 610054, P.R. China
² International Centre for Materials Physics, Chinese Academy of Sciences, 110016 Shenyang, P.R. China

Corresponding author: shaoyi_wu@163.com

Received: 10 March 2009
Revised: 26 May 2009
Accepted: 28 May 2009
Published online: 17 September 2009

Abstract

The defect structure and the EPR parameters (the g factors, the hyperfine structure constants and the superhyperfine parameters) for the tetragonal Ir²⁺ center in AgBr are theoretically investigated using the perturbation formulas of these parameters for a 5d⁷ ion in tetragonally elongated octahedra. In the calculations, the contributions from the ligand orbital and spin-orbit coupling interactions and the local lattice (elongation) distortion due to the Jahn-Teller effect are taken into account. Related molecular orbital coefficients and the ligand unpaired spin densities are determined quantitatively using a cluster approach. The impurity center is attributed to the substitutional [ IrBr₆] ⁴⁻ cluster on host Ag⁺ site, which suffers the relative elongation of about 0.08 Å along C₄ axis due to the Jahn-Teller effect. The calculated EPR parameters based on the above Jahn-Teller elongation show good agreement with the observed values.