Theoretical investigation of the spin hamiltonian parameters for the tetragonal [Fe(CN)4Cl2]5 - Complex in NaCl

摘要

The spin Hamiltonian parameters (the g factors and the superhyperfine parameters) for the tetragonal [Fe(CN) _4Cl _2] ~5- complex in NaCl are theoretically investigated from the perturbation formulas of these parameters for a low spin (S=1/2) 3d ~7 ion in tetragonally elongated octahedra. This impurity center is attributed to the substitutional Fe ~(2+) (in the form of [Fe(CN) _6] ~4-) on host Na ~+ site reduced by capturing one electron during the X-ray irradiation process, with the two axial ligands CN ~- replaced by two Cl ~-. Since the crystal fields of the axial ligands Cl ~- are weaker than those of the perpendicular ligands CN -, the [Fe(CN) _4Cl _2] ~5- complex exhibits a tetragonally elongated octahedron. This system shows the low spin S=1/2 of the strong crystal field case, which is unlike the high spin S=3/2 of the weak and intermediate crystal field case for Fe ~+ in conventional chlorides. The theoretical spin Hamiltonian parameters are in reasonable agreement with the experimental data, and the results are discussed.