Influence of Milling Treatment by Mechanofusion Apparatus on Magnetic Properties of Sr-Ferrite Powder and the Compacts

To investigate effects of shear stress and shear strain on the magnetic properties of Sr-ferrite powder, the powder was milled by a mechanofusion (MF) apparatus, and its magnetic characteristics were studied. Coercive force of the MF-milled powder was decreased with milling time, and it reached the constant value of 140 kA⋅m-1 as milling time was longer than 30 min. Reduction of the coercive force of the milled powder was found to slightly improve degree of powder particle alignment under applied magnetic fields. M-type ferrite phase of the original Sr-ferrite powder remains unchanged after the MF-milling treatment. The mean particle size of the powder was increased by a MF-milling treatment longer than 30 min due to aggregation of the powders. As a result, the optimum MF-milling time was in the range from 15 min to 30 min under the experimental conditions of this study.