Polarized-Neutron Study of the Magnetic Moment Density in Antiferromagnetic CuSO4

A determination of the spatial distribution of magnetic moment density in the antiferromagnet CuS${\mathrm{O}}_4$ has been made by means of the polarized-neutron-beam technique. Data collected at 4.5°K for two zones showed very large deviations in a number of cases from a smooth form-factor curve. Fourier transforms of the data revealed regions of substantial magnetic moment density ($\sim 0.05-0.1{\mu }_B$) localized mainly between the ${\mathrm{Cu}}^{2+}$ ions and the S${\mathrm{O}}_4^{2-}$ groups. The observation of appreciable concentrations of density in positions removed from the ${\mathrm{Cu}}^{2+}$ sites suggests the presence of relatively strong superexchange interactions through the S${\mathrm{O}}_4^{2-}$ groups, as indicated also by the relatively high Néel point of about 36°K. In order to permit accurate analysis of the polarized-beam data, the crystal-structure parameters of CuS${\mathrm{O}}_4$ at 77°K were refined by least-squares analysis, and the errors in the calculated nuclear-structure factors were evaluated.