Theoretical investigations of the spin Hamiltonian parameters and local tetragonal distortions for Cu in crystalline and amorphous TeO 2 and GeO 2.

The spin Hamiltonian parameters (i.e., anisotropicgfactors and hyperfine structure constants) and local tetragonal distortions for Cu2+in crystalline and amorphous TeO2and GeO2are theoretically investigated using the high-order perturbation formulas of these parameters for a tetragonally elongated octahedral 3d9cluster. The impurity Cu2+occupying the octahedral sites are found to experience the relative tetragonal elongation ratios of about 11.4% and 9.5% for crystalline TeO2and GeO2and 10.8% and 6.6% for amorphous TeO2and GeO2, respectively, along the C4axis due to the Jahn–Teller effect. This reveals the larger tetragonal elongation distortions for the Cu2+centres in crystalline than amorphous systems (especially TeO2). The theoretical spin Hamiltonian parameters show good agreement with the experimental data. The results are discussed. [ABSTRACT FROM AUTHOR]