(Zn, Ni, Ti) substituted barium ferrite particles with improved temperature coefficient of coercivity

TLDR: In this article, it was shown that the coercivity, H c, of Ba-ferrite particles is mainly controlled by the crystalline anisotropy, and that the substitution of Fe 3+ ions by Zn 2+, Ni 2+ and Ti 4+ ion will affect the saturation magnetization σ s, coercivity H c and their temperature coefficients.

Abstract: The Ba-ferrite particles have a positive temperature coefficient of d H c /d T . From the viewpoint of recording system applications, the d H c /d T should be reduced in order to improve the operating margin for temperature change. It was shown that the coercivity, H c , of Ba-ferrite particles is mainly controlled by the crystalline anisotropy. In the Ba-ferrite there are five distinct crystallographic sites or sublattices, and the Fe 3+ ion located on different site has different contribution to crystalline anisotropy. The replacement of Fe 3+ ions by Zn 2+ , Ni 2+ , and Ti 4+ ion will effect on the saturation magnetization σ s , coercivity H c and their temperature coefficients. The Zn–Ti, Ni–Ti, and Ni–Zn–Ti substituted Ba-ferrite particles were investigated. It was found that the Zn–Ti substituted Ba-ferrite particles have higher σ s , but large temperature coefficient of coercivity d H c /d T . In the case of Ni–Ti and Ni–Zn–Ti substitution the d H c /d T could be reduced to a small value, near to zero or negative value, while the σ s decreases very slowly with increasing the amount of substitution.