Effects of Ga Substitution on Crystallographic and Magnetic Properties of Co Ferrites

The crystallographic and magnetic properties of gallium-substituted cobalt ferrite (CoGaxFe2-xO4) were investigated. The new material was synthesized using conventional ceramic methods, with gallium substituted for ferrite in the range of x = 0.0 to 1.0, in steps of 0.2. X-ray diffraction and Mossbauer spectroscopy were used to confirm the presence of crystallized particles in the CoGaxFe2-xO4 ferrite powders. All of the samples exhibited a single phase with a spinel structure, and the lattice parameters decreased as the gallium content increased. The particle size of the samples also decreased as gallium increased. For x <= 0.4, the Mossbauer spectra of CoGaxFe2-xO4 could be fitted with two Zeeman sextets, which are the typical spinel ferrite spectra of Fe3+ with A- and B-sites. However, for x >= 0.6, the Mossbauer spectra could be fitted with two Zeeman sextets and one doublet. The variation in the Mossbauer parameters and the absorption area ratio indicated a cation distribution of (Co0.2-0.2xGaxFe0.8-0.6x)[Co0.8+0.2xFe1.2-0.4x]O-4, and the magnetic behavior of the samples suggested that the increase in gallium content led to a decrease in the saturation magnetization and in the coercivity.