Crystallographic and magnetic properties of In0.1Cu0.45Fe0.45Cr2S4

In0.1Cu0.45Fe0.45Cr2S4 has been studied by Mossbauer spectroscopy, X-ray di ffraction, and magnetic-susceptibility measurements. The crystal is found t o have a cubic spinel structure with the lattice constant a(0) = 9.931 +/- 0.005 Angstrom. The iron ions are in ferric states. The temperature depende nce of the magnetic hyperfine field is analyzed by the Neel theory of ferri magnetism. The intersublattice superexchange interaction is antiferromagnet ic with a strength of J(AB) = -4.90 k(B) while the intrasublattice superexc hange interactions are ferromagnetic with strengths of J(AA) = 7.90 k(B) an d J(BB) = 10.30 k(B). The ferrimagnetic-to-paramagnetic transition takes pl ace at 231 K. There is a second transition from the ferrimagnetic state to a spin-glass-like state below 78 K. A ten percent (10 %) replacement of the Cu-Fe ion-pairs by In ions decreases the Neel temperature by 34 % and the magnetic hyperfine field at liquid-helium temperature by 12 %.