Surface effect on saturation magnetization of Co and Ti substituted Ba-Ferrite fine particles

The surface effect on saturation magnetization of Co and Ti substituted Ba-ferrite platelet fine particles is reported. The saturation magnetization decreases linearly with increasing hexagonal c-plane surface area of the particles, and the effect of the side plane surface area on the saturation magnetization is negligible. This result indicates that a low saturation magnetization layer exists predominantly on the c-plane surfaces. The saturation magnetization of the c-plane surface layers increases noticeably with decreasing temperature, and approaches the saturation magnetization value for the bulk Ba-ferrite. The low saturation magnetization at the surface layer is explained by a thermal fluctuation effect on the magnetic ions at the surface layer which have a weaker exchange field than the ions inside the particles. Therefore, particles with small diameter to thickness ratio values are beneficial in obtaining higher saturation magnetization under a given particle volume.