Theoretical investigations of the local structure and the spin Hamiltonian parameters for Ti2+ in MgCl2

The local structure and spin Hamiltonian parameters (zero-field splitting and g factors) for Ti2+ in MgCl2 are theoretically studied using the perturbation formulas of these parameters for a 3d2 ion under trigonally distorted octahedra. The contributions from the dynamical Jahn-Teller effect, the configuration interactions and the ligand orbital and spin-orbit coupling interactions are quantitatively involved based on the cluster approach in a uniform way. The chlorine polyhedron around the impurity Ti2+ is found to transform from a slightly compressed octahedron in pure MgCl2 to a slightly elongated one, characterized by the local angular decrease of 0.3° related to the host bond angle 54.78° due to the Jahn-Teller effect. The calculated spin Hamiltonian parameters based on the above trigonal elongation show good agreement with the experimental data. The results are discussed.