Spin Hamiltonian parameters and local structures for Co 2+ ions in calcite-type trigonal carbonates MCO 3 (M=Co, Cd and Ca)

Abstract

From the perturbation formulas based on the cluster approach for 3d 7 ion in trigonal octahedral sites of crystals, the spin Hamiltonian parameters ( g factors g  , g ⊥ and hyperfine structure constants A  , A ⊥) for Co 2+ in calcite-type MCO 3 (M=Co, Cd, Ca) crystals are calculated. In the calculations, for CoCO 3 crystal, the structural data of pure crystal are used, whereas for the Co 2+-doped CdCO 3 and CaCO 3 crystals, the local structural data caused by the impurity-induced local lattice relaxation are considered. The calculated results show good agreement with the observed values obtained from electron paramagnetic and antiferromagnetic resonance experiments. The difficulty shown in the previous paper related to the g ⊥ value of CoCO 3 obtained from the change of the g factor as a function of the crystallographic data (i.e., the unit cell parameters) a 0 and α 0 of pure MCO 3 crystals is removed.