Preparation of strontium W-type hexaferrites in a low oxygen pressure and their magnetic properties

We report a successful preparation of strontium W-type hexaferrite (SrW: SrFe18O27) without a quenching method in a reduced oxygen atmosphere and its magnetic properties. The pure SrW poly-crystalline samples except their surface layer could be prepared by solid state reaction at 1300-1315 degrees C and subsequent furnace-cooling to room temperature in a low oxygen partial pressure of 10(-3) atm. Assintered SrW samples exhibited soft magnetic properties possessing high saturation magnetization values of 78.8(8)-81.3(8) emu/g and low coercivity values below 100 Oe. With increasing the sintering temperature, both saturation magnetization and anisotropy field values of samples were increased, which is attributable to an increased ratio of Fe2+/Fe3+ ions in the SrW phase induced by enhanced oxygen deficiency. (C) 2016 Elsevier B.V. All rights reserved.