Nuclear Electric-Field-Gradient Determination in Single Crystals of Fe(NH4SO4)2·6H2O and FeSO4·7H2O

Abstract

Single-crystal Mössbauer studies have been carried out on Fe${\left(\mathrm{N}{\mathrm{H}}_4\mathrm{S}{\mathrm{O}}_4\right)}_2$·6${\mathrm{H}}_2$O and FeS${\mathrm{O}}_4$·7${\mathrm{H}}_2$O to determine the five independent parameters of the nuclear electric-field-gradient (EFG) tensor, viz., its principal values, asymmetry parameter, and coupling constant, and the direction cosines of the EFG axes with respect to the crystal axes. Furthermore, in view of the agreement of the observed and calculated values of the absorption-peak-area ratios, the anisotropy of the Lamb-Mössbauer fraction for both these cases does not appear to be significant. It is concluded that in the case of Fe${\left(\mathrm{N}{\mathrm{H}}_4\mathrm{S}{\mathrm{O}}_4\right)}_2$·6${\mathrm{H}}_2$O, the principal axes of the EFG tensor are not coincident with those of the susceptibility tensor.