Superexchange interactions in inverse spinel lithium ferrites

Spinel ferrites, MFe2O4 (M = Ni, Mg, Co, Li) samples were prepared by sol-gel method. It has been studied by X-ray diffraction, Mossbauer spectroscopy. X-ray diffraction patterns were analyzed by the Rietveld refinement. The samples have been cubic spinel structure with the lattice constant (a(0)) is 8.326 similar to 8.390 angstrom. The temperature dependence of the magnetic hyperfine field is analyzed by the Neel theory of ferrimagnetism. The intersublattice A-O-B and intrasublattice A-O-A superexchange interactions are found to be antiferromagnetic while the intrasublattice B-O-B superexchange interaction is ferromagnetic for the MFe2O4 (M = Ni, Mg, Co) samples as shown in Table 1. On the other hand, the intersublattice superexchange interaction is found to be antiferromagnetic while the intrasublattice superexchange interactions are ferromagnetic for the lithium ferrite sample.