Hyperfine interactions and magnetic properties of nanosized powders of magnetite

摘要

The fine powder of magnetite Fe3O4 was obtained by precipitation of aqueous solutions of chemically pure Mohr's salt Fe(NH4)2(SO4)2·6H2O and FeCl3 using concentrated NH4OH. The fine powders with the particle size from 5 to 25 nm were obtained. Some portions of powders were subjected to heat treatment in air at temperatures of 473, 573 and 673 K. This annealing leads to the formation of λ-Fe2O3. The parameters of hyperfine interactions for these ions in the crystal structure of Fe3O4 and γ-Fe2O3 by the nuclear gamma-resonance method (NGR) were obtained and difference in occupations of iron ions in octa- and tetra-sublattice compared to stoichiometric magnetite was revealed.