Preparation and Magnetic Properties of Co2Z Hexaferrite From Annealed Mixtures of BaM and Co2Y Hexaferrite Precursor Powders

The transformation of fine mixtures of BaM and Co2Y hexaferrite powders to Co2Z hexaferrite has been studied by scanning electron microscopy (SEM), x-ray diffraction (XRD), and vibrating sample magnetometry (VSM) measurements. The precursor hexaferrites were prepared by a solution-phase auto-combustion method and subsequently mixed in a low energy rolling mill. The BaM/Co2Y mixtures were annealed at temperatures between 800 and 1300 \r{ }C in air for 2 hours. Over this temperature range a rapid decrease in the measured coercivity from a value of about 4 kOe, characteristic of the hard BaM component of the mixture, to a value of about 50 Oe, characteristic of the magnetically soft Co2Z phase, was observed. The coercivity reduction was accompanied by a modest increase in the saturation magnetization to a value of about 60 emu/g.