Structural and magnetic properties of BaFe12-2xTixRuxO19

Barium hexaferrite samples BaFe12-2xTixRuxO19 were prepared by ball milling and their structural and magnetic properties were investigated using X-ray diffraction, TEM, Moessbauer spectroscopy, and vibrating sample magnetometry. It was found that the particle size increases appreciably, and the crystallinity improves with Ti-Ru substitution. Moessbauer spectroscopy revealed that the substitution of Fe3+ ions occurs at the 4f2 and 4f1 + 2a sites for low substitution, and substitution at the 2b site occurs for x ≥ 0.2. The saturation magnetization increases up to x = 0.2, and then starts to decrease for higher x values, while the coercivity decreases monotonically, recording a reduction of 55% at x = 0.4. These results were interpreted in terms of the site preferential occupation of the Ti2+ and Ru4+ ions. The thermomagnetic curves for all samples showed Hopkinson peaks indicating the presence of small superparamagnetic particles in the samples. The sample with x = 0.0 was found to consist of purely superparamagnetic particles, while the substituted samples were found to contain only 22-30% of the powders' mass as superparamagnetic particles.