Magnetoplumbite and W-type barium ferrites as magnetic mixture with hematite

概要

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Magnetic properties were studied on polycrystalline composite mixtures of magnetoplumbite-type BaFe_<12>O_<19> and W-type BaCo_2Fe_<16>O_<27> ferrites with α-Fe_2O_3. The respective ferrite mixtures were prepared with hematite in 0 to 70mol% using solid state reaction. X-ray diffraction (XRD) analysis and magnetic measurement suggested the products were simple mixtures of the ferromagnetic BaFe_<12>O_<19> or BaCo_2Fe_<16>O_<27> with α-Fe_2O_3 even after sintering at 1250℃. Their magnetization decreased with the increasing contents of α-Fe_2O_3. Their electrical resistivities of higher than 10^2Ωm were too large to observe their magnetic field dependence, magnetoresistance (MR) effect. Electrical resistivity decreased to 0.36Ωm by the post annealing of the as prepared BaCo_2Fe_<16>O_<27> with a small amount of α-Fe_2O_3 in Ar at 1000℃ for 5h. The improved electrical conductivity in 4 orders of magnitude showed the MR effect of 0.86% on the post annealed BaCo_2Fe_<16>O_<27> product.
2009-01-01