材料期刊网

The empirical superposition model has been used to analyse the zero-field splitting of 3d5(Mn2+, Fe3+) ions in crystals with approximately C3v symmetry. The negative signs of intrinsic parameters b2BAR(R0) for these crystals are the same as the normal b2BAR(R0) which is obtained from the 3d' ions in many oxygen octahedra. The magnitude of b2BAR(R0) for Mn2+ or Fe3+ ion in the case of isocharge substitution is consistent with the respective normal value of Mn2+ or Fe3+ ion. Whereas in the case of charge misfitting substitution, the small disparity of b2BAR(R0) is found between the calculated and normal values. This can be attributable to the local lattice relaxation caused by the fact that the interacting forces between impurity and ligands are different from those of host crystals. It appears that the anomaly related to the signs of b2BAR in Al2O3:Fe3+, MgTiO3:Mn2+ and MgTiO3:Fe3+ crystals pointed out by some researchers does not exist and the empirical superposition model is applicable to 3d5 ions in C3v symmetry.