Conditions for synthesizing single phase materials of the hexagonal Z-type were investigated by preparing samples with various compositions (x=0, 0.2, 0.4, 0.6 in Ba3Co2-xFe24+xO41) and oxygen partial pressures, PO2=21.3, 31.3, 41.3, 61.3, 101.3 kPa, at T=1573 K. The phases formed in the samples were examined by X-ray diffraction technique and the dc magnetization was measured as a function of temperature by a vibrating sample magnetometer (VSM) at a magnetic field of 5.6 kA/m. The correlation between the phases occurring in the samples and the complex permeability μ, at 100MHz was investigated, and it was indicated that high μr is obtained when the hexagonal Z-type occurs without any other phase. The highest μr=20 was obtained with conditions of x =0.2, PO2=101.3 at 1573 K. The neutron diffraction patterns were measured between 294 and 773 for the sample of x=0.4. Two significant magnetic Bragg reflections were observed in the pattern measured at 294 K, but no peak at 773 K. Integrated intensities of the magnetic scattering peaks were plotted against temperatures, which was consistent with the magnetization vs. temperature curve measured with VSM. It was indicated that the hexagonal Z-type phase exhibits two stage magnetic transition at 500-540 and 680 K.
