Temperature Dependence of Magnetic Properties in Ferrite Powders by High Energy Ball Milling

Abstract

The ferrite powders were prepared by high energy ball-milling, and subsequently compacted under a pressure of 490MPa for 3min and sintered at 1273~1673K for 3h. The spherical shaped initial powders with a mean size of approximately 70μm were changed to irregular shaped powders of 230nm in a mean size after milling at 300rpm for 3h. The milled powders were composed of the nanosized particles with a size of approximately 10nm. After compacting, the green density was approximately 70%. The sintered sample with a relative density of approximately 98% was obtained by sintering at 1473K, which showed the saturation magnetization (Ms) of approximately 90emu/g and the coercivtity (Hc) of approximately 19Oe at room temperature. The Ms decreased with increasing temperature, whereas the Hc and initial permeability (μi) were unchanged. There was no change in the Ms, Hc and μi during holding at 423K.