Studies on the local structures and spin Hamiltonian parameters for the rhombic Nb4+ centers in MO2 (M = Sn, Ti and Ge) crystals
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: email@example.com
Accepted: 29 November 2010
Published online: 28 January 2011
The local structures and the spin Hamiltonian parameters for the substitutional Nb4+ centers in MO2 (M = Sn, Ti and Ge) crystals are theoretically studied using the perturbation formulas of these parameters for a 4d1 ion in a rhombically compressed octahedron. The above Nb4+ centers are found to experience the Jahn-Teller distortions, characteristic of the relative axial compressions (~ 0.01–0.02 Å) and the non-axial (planar) angular increases (~ 3°). As a result, the ligand octahedra are transformed from original elongation on host tetravalent cation sites to compression in the impurity centers, with additional non-axial distortions smaller than those in the hosts. The influences of the Jahn-Teller distortions and the ligand orbital contributions are also analyzed.
© EDP Sciences, 2011