Study on the Increase of Co Concentration and the Purification of LaCo Cosubstituted M-Type Sr Ferrite by Oxygen Partial Pressure Control

Abstract

The LaCo cosubstituted M-type strontium ferrite attracts attention as a base material for high-performance ferrite magnets. It is known that the uniaxial magnetic anisotropy of the material is enhanced by increasing the amount of Co by heat treatment under high oxygen pressure, but there is a problem in obtaining a pure sample. The present study investigated the conditions to obtain a single phase with increased LaCo substitution by heat treatments under several oxygen pressures. A single phase of M-type ferrite was obtained up to x = 0.35 at pO2 = 1 atm, and up to x = 0.65 at pO2 = 10 atm with the composition formula of Sr11xLaxFe121xCoxO19. The magnetic anisotropy is enhanced according to the Co concentration in these samples.