Neutron-Diffraction Investigation of Cu${\mathrm{Cr}}_2$${\mathrm{Se}}_4$ and Cu${\mathrm{Cr}}_2$${\mathrm{Te}}_4$

Neutron-diffraction measurements at 508°K as well as x-ray-diffraction measurements at room temperature show the compounds Cu${\mathrm{Cr}}_2$ ${\mathrm{Te}}_4$ and Cu${\mathrm{Cr}}_2$ ${\mathrm{Se}}_4$ to have a normal spinel structure. The coherent scattering length of Se was found to be 0.779×${10}^{-12\mathrm{}}$ cm. The neutron-diffraction diagrams below the transition temperature confirm the ferromagnetic behavior proposed by Lotgering. The magnetic moment of the Cu ion in the tetrahedral site is zero, whereas the magnetic moments of the Cr ions in the octahedral site are approximately three Bohr magnetons, corresponding with ${\mathrm{Cr}}^{3+}$.