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A solid-solid equilibrium sintering method is used for fabricating quasi-single crystal barium hexaferrite with low microwave loss. The properties of these crystals have made them ideal for use at U-band frequencies and hence the utilization of the materials has potential to reduce costs for microwave devices.

Ba[Fe.sub.12][O.sub.19] hexaferrite thick films having high hysteresis loop squareness and low ferromagnetic resonance (FMR) linewidths are processed through the use of a screen printing technique coupled with hot-press sintering. The results have shown that the narrow linewidths can be attributed to the reduction in porosity and the improvement in c-axis orientation of crystallites in polycrystalline barium ferrite films.

Hexagonal BaFe12O19 ferrite films, having thicknesses ranging from 200–500 μm, were prepared by a screen printing process followed by sintering heat treatments. Structural, magnetic, and microwave measurements confirmed that the polycrystalline films were suitable for applications in self-biasing microwave devices in that they exhibited a large remanence (4πMr=3800 G), high hysteresis loop squareness (Mr/Ms=0.96) and low microwave loss. A derivative linewidth ΔH of 310 Oe was measured at 55.6 GHz. This represents the lowest ΔH measured in polycrystalline hexaferrite materials. ΔH can be further improved by reducing porosity and improving the c-axis orientation of grains in polycrystalline ferrite. [ABSTRACT FROM AUTHOR]