Theoretical investigations of the spin Hamiltonian parameters and local tetragonal distortions for Cu2+ in crystalline and amorphous TeO2 and GeO2

Abstract

The spin Hamiltonian parameters (i.e., anisotropic g factors and hyperfine structure constants) and local tetragonal distortions for Cu2+ in crystalline and amorphous TeO2 and GeO2 are theoretically investigated using the high-order perturbation formulas of these parameters for a tetragonally elongated octahedral 3d9 cluster. 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 TeO2 and GeO2 and 10.8% and 6.6% for amorphous TeO2 and GeO2, respectively, along the C4 axis 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.