Electron Spin Resonance of Mn2+ Impurities in Blodite

Abstract

The electron spin resonance of Mn2+ impurities in natural crystals of blodite, 2(Na2Mg(SO4)2∙4H2O), was studied at ~9.2 GHz and at ~290 °K. Two differently oriented, but otherwise equivalent, magnetic complexes of Mn2+ were found. The complexes are related to each other by two-fold symmetry about the crystallographic b axis. The resonance line positions were fitted to a spin Hamiltonian of rhombic symmetry and the following parameters were determined: g = 1.9993 ± 0.0005, b20°= 334.0 ± 1.5, b22 = 260.0 ± 1.5, b40 = 1.2 ± 0.2, A = 89.0 ± 1.0, and B = 86.4 ± 0.5. The values of bnm, A, and B are in units of 104 cm−1. The magnitudes of the A and B hyperfine parameters were used to calculate covalency in crystals containing Mn2+ coordinated by mixed types of ligands. The covalency analysis was extended to crystals which contain two different sites with the same type of ligands. This analysis enabled us to determine which of the Mn2+ magnetic complexes reported for diopside belong to a Ca or a Mg site.