MAGNETIC-PROPERTIES OF MODIFIED BA-FERRITE PARTICLES

Modification with magnetite on Ba-ferrite particles was carried out by heating alkaline suspension including Ba-ferrite particles and Fe2+ hydroxides as described by Kiyama et al. [J. Solid State Chem. 99, 329 (1992)] to get higher magnetization. As a result of x-ray powder diffraction measurements, reflection intensity of magnetoplumbite phase decreases and that of spinel phase increases with increase of Fe2+ quantity added, simultaneously. Coercive force goes down and magnetization increases as Fe2+ quantity added increases. The differential hysteresis loop of the mixed samples (Ba-ferrite particles and magnetite particles) has two peaks. And that of the modified samples has only one peak. From these results, it becomes clear that there exists strong magnetic interaction between Ba-ferrite core and magnetite shell. The measurements of temperature dependence of magnetization at the applied field of about 16.5 kA/m shows that the Hopkinson peak shifts toward higher temperature with increase of the modified amount. It also indicates the strong magnetic interaction between core and shell materials.