Eur. Phys. J. Appl. Phys. 50, 30901 (2010)
https://doi.org/10.1051/epjap/2010052

Investigations of the EPR parameters and local structures for the substitutional Cu²⁺ centers in the tungstates

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, Shenyang 110016, P.R. China

Corresponding author: shaoyi_wu@163.com

Received: 8 July 2009
Revised: 5 February 2010
Accepted: 12 March 2010
Published online: 23 April 2010

Abstract

The high order perturbation formulas of the electron paramagnetic resonance (EPR) parameters (the g factors and the hyperfine structure constants) are established for a 3d⁹ ion in orthorhombically compressed octahedra. These formulas are applied to the investigations of the EPR spectra and local structures for the substitutional Cu²⁺ centers in the wolframite-type tungstates AWO₄ (where A = Cd, Zn, Mg). Based on the studies, the [CuO₆]^10- clusters are found to experience the local planar bond length variations δR' (≈0.096, 0.021 and 0.028 Å for CdWO₄, ZnWO₄ and MgWO₄, respectively) along X and Y-axes. These values are quite different from the host planar bond length variations δR (≈0.013, 0.069 and 0.005 Å) for the A²⁺ sites in the pure tungstates. The above local bond length variations in the impurity centers can be attributed to the Jahn-Teller effect and size mismatching substitution. The theoretical EPR parameters based on the above local structures agree well with the experimental data. By adopting the uniform theoretical formulas and fewer adjustable parameters in this work, the improvements are achieved for the EPR parameters as compared with the previous calculation results.