Development of high-saturation magnetization spinel copper ferrite

The copper ferrite phase (Cu_0.5 Fe_2.5O₄) has a spinel structure with copper normally occupying both the tetrahedral (A) site and the octahedral (B) site, depending on its valence. Theoretically, the material with all copper in the monovalent state and occupying the A-site of the spinet sublattice, will have a very high saturation magnetization of 7.5μ_B (11,000 Gauss). This study was undertaken to examine various ways to obtain a high saturation magnetization in the ferrite of the above composition. Samples of the Cu_0.5Fe_2.5O₄ phase were heated at different temperatures between 12000°C and 1350°C in air and quenched in oil. Mossbauer spectroscopy, resistivity, saturation magnetization and x-ray lattice parameter measurements obtained on the powders revealed a structure property relationship. With the help of this structure-property relationship and making use of a high temperature dynamic x-ray diffractometer (HT-DXRD), experiments were performed to stabilize the copper ferrite with cations in the fight configuration. Evidence of ordering of the monovalent copper to the A-site of the spinet structure at temperatures between 1170°C and 1200°C in highly reducing atmosphere is presented. This study also describes an independent method using anomalous synchrotron scattering followed by Rietveld analysis to obtain cation configuration in a rapidly quenched copper ferrite.; Nanocrystalline copper ferrite powders were also synthesized, at low temperatures, using a forward strike gelation method with polyacrylic acid (PAA) as gelating agent. The effect of pH and the ratio of the cation to the carboxylic group in the initial gel were studied with respect to both the phases and crystallite size of the final powders synthesized. The reactions occurring in the nanophase copper ferrite, both in air and in reducing atmosphere, are outlined with the help of the HT-DXRD system.; Results are also presented on the substitution of cations with specific site preference; of Zn+2 (the A-site) and of Li+1 (the B-site) in the spinel structure of the copper ferrite system. Effect of the substitution on the magnetic property, structure (lattice parameter) and microstructure of the bulk ferrites are outlined. Bulk specimen made from precursors obtained by conventional solid state technique and chemical (organic gelation) synthesis are also compared in terms of densities and microstructures.