Effect of Microstructure in the Vicinity of Ferrite Grain Surface on Coercivity in Ca-La-Co M-type Ferrite Magnets

Abstract

The effect of microstructure in the vicinity of ferrite grain boundary in Ca-La-Co M-type ferrite on coercivity was investigated. According to Spherical Aberration Corrected Scanning Transmission Electron Microscopy (Cs-STEM) analysis, the Ca concentration in the vicinity of ferrite grain surface of the sintered body prepared under rapid cooling was found to be lower than that in a sintered body prepared under gradual cooling at the rate of −300 K/h. Considering that Co concentration was high in the region where Ca concentration was low as was found by Electron Probe Micro Analyzer (EPMA) analysis, it is suggested that the Co concentration was high in the vicinity of the ferrite grain surface prepared under rapid cooling, thereby enhancing crystal magnetic anisotropy in the vicinity of ferrite grain surface, which contributed to improvement of coercivity.