Abstract The spin Hamiltonian parameters (SHPs) (g factors and zero-field splittings (ZFSs) D and E) and the local structure for Cr3+ in K2PdCl4 single crystal are theoretically investigated from the perturbation calculations of the SHPs for an orthorhombically distorted octahedral 3d3 cluster. The impurity Cr3+ is found not to occupy the conventional square planar Pd2+ site but to locate at the octahedral K+ site, associated with the relative axial compression ratio ρ( ≈ 11.1%) and the perpendicular bond length variation ratio τ( ≈ 11.7%). The impurity centre exhibits much smaller axial compression distortion and much larger perpendicular orthorhombic distortion than the host K+ site in K2PdCl4 ρ H ≈ 18.6% and τ H ≈ 0) and hence a more regular ligand octahedron, corresponding to the very small ZFSs. The contributions to g-shifts Δ g C T from the CT mechanism are opposite in sign and twenty-one times larger in magnitude compared with Δ g C F from the CF mechanism. For the ZFSs, the CT contributions DCT and ECT are opposite in sign and almost the same in magnitude with respect to the corresponding DCF and ECF.

The electron paramagnetic resonance (EPR) parameters (g factors and the hyperfine structure constants) for Ni2+ and Co+ in MgO are theoretically studied from the perturbation formulas of these parameters for a 3d8 ion in octahedral crystal-fields. In the computations, the ligand orbital and spin-orbit coupling contributions are taken into account using the cluster approach. The calculated EPR parameters are in good agreement with the experimental data. The larger g factor and the smaller magnitude of the hyperfine structure constant for Ni2+ as compared with those for Co+ can be attributed to the higher spin-orbit coupling coefficient and the lower dipolar hyperfine structure parameter of the former, respectively.