Mossbauer study of Li0.5Fe2.5O4

Li0.5Fe2.5O4 has been studied by means of Mossbauer spectroscopy and x-ray diffraction. The crystal is found to have a cubic spinel structure with the lattice constant a(0) = 8.344 +/- 0.005 Angstrom. The iron ions are in ferric states. The temperature dependences of the magnetic hyperfine fields at the Fe-57 nuclei at the tetrahedral (A) and octahedral (B) sites are analysed using the Neel theory of ferrimagnetism. The intersublattice superexchange interaction is found to be antiferromagnetic with a strength of J(A-B) = -10 8k(B) while the intrasublattice superexchange interactions are ferromagnetic with strengths of J(A-A) = 17.6k(B) and J(B-B) = 17.8k(B). The Debye temperatures of the tetrahedral and octahedral sites are determined to be 398 +/- 5 K and 362 +/- 5 K, respectively.