Mossbauer studies of superexchange interaction in tetragonal CuFe2O4

CuFe2O4 has been studied by Mossbauer spectroscopy and X-ray diffraction. The crystal is found to have a tetragonal spinel structure with the lattice constants a(0)=(5.805+/-0.005) Angstrom and c(0) = (8.669 +/- 0.005) Angstrom. The iron ions are in ferric Fe3+ states. The temperature dependence of the magnetic hyperfine fields at Fe-57 nuclei at the tetrahedral (A) and octahedral (B) sites is analyzed by the Neel theory of ferrimagnetism. The intersublattice superexchange;interaction is found to be antiferromagnetic with its strength of J(A-B) = -19.5/k(B) while intrasublattice superexchange interactions are ferromagnetic with their strengths of J(A-A) = 3.1k(B) and J(B-B) = 4.4k(B).