Investigation of the spin Hamiltonian parameters of a tetragonal VO2+ center in (NH4)2SbCl5

The spin Hamiltonian parameters g(parallel to) and g(perpendicular to) and the hyperfine structure constants A(parallel to) and A(perpendicular to) of a tetragonal VO2+ center in (NH4)(2)SbCl5 are investigated, using the perturbation formulas for a 3d(1) ion in tetragonally compressed octahedra. In these formulas, the contributions to the spin Hamiltonian parameters from the s- and p-orbitals as well as the spin-orbit coupling coefficient of the Cl- ligand are taken into account, based on the cluster approach. According to these studies, compression of the ligand octahedra results from the strong axial crystal-fields due to the short V4+-O2- bond in the [VOCl4](2-) cluster. The obtained spin Hamiltonian parameters agree well with the experimental data and need fewer adjustable parameters than the previous studies. The covalency of the studied system is also discussed.