Improving magnetic properties of barium hexaferrites by La or Pr substitution

Anisotropic magnetic nanoparticles: A review of their properties, syntheses and potential applications

Preparation and magnetic properties of (Zn-Sn) substituted barium hexaferrite nanoparticles for magnetic recording

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.

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

Co‐Sn substituted barium ferrite particles, BaFe12−2xCoxSnxO19 (0≤x≤1.4), have been investigated using x‐ray, VSM, and Mossbauer spectroscopy. The magnetocrystalline‐anisotropy constant has been determined as a function of x from an analysis of the approach to magnetic saturation. Mossbauer spectra indicate that Co2+ and Sn4+ ions have a strong preference for the 2b, 4fVI, and 12k sites. The reduced anisotropy constants k=K1(x)/K1(0) have been calculated based on the single‐ion model and the site preferences and agree well with the measured values. The origin of the magnetic changes caused by Co2+ and Sn4+ substitution can be attributed to the site preferences.

Sheng-Li Geng

Papers

Morphological, structural and magnetic characteristics of Co-Ti and Co-Sn substituted Ba-ferrite particles for magnetic recording

STRUCTURAL AND MAGNETIC PROPERTIES OF Co-Sn SUBSTITRTED Ba-FERRITE PARTICLES FOR MAGNETIC RECORDING