Oriented barium hexaferrite thick films with narrow ferromagnetic resonance linewidth

Hexagonal BaFe 12 O 19 ferrite films, having thicknesses ranging from 200 - 500 μ m , 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 ( 4 π M r = 3800 G ) , high hysteresis loop squareness ( M r ∕ M s = 0.96 ) and low microwave loss. A derivative linewidth Δ H of 310 Oe was measured at 55.6 GHz. This represents the lowest Δ H measured in polycrystalline hexaferrite materials. Δ H can be further improved by reducing porosity and improving the c -axis orientation of grains in polycrystalline ferrite.