Screen printed thick self-biased, low-loss, barium hexaferrite films by hot-press sintering

Abstract

Ba Fe 12 O 19 hexaferrite thick films having high hysteresis loop squareness (Mr∕Ms) and low ferromagnetic resonance (FMR) linewidths were processed through the use of a screen printing technique coupled with hot-press sintering. Scanning electron microscopy and x-ray diffraction measurements exhibit strong crystallographic c-axis alignment of crystals perpendicular to the film plane. Static magnetic resonance and FMR measurements were performed to determine the effect of the preparation technique on magnetic hysteresis and microwave properties. Hot pressing during sintering produced dense thick films having high squareness (>0.95) and reduced coercivity (∼1900Oe). Of greater importance was the measurement of a minimum peak-to-peak FMR linewidth, 320Oe at the U band, for films ranging in thickness from 100to500μm. Theoretic estimates suggest that such narrow linewidths can be attributed to the reduction in porosity and the improvement in c-axis orientation of crystallites in polycrystalline barium ferrite films. As such, haxaferrite materials prepared using this technique offer opportunities in the next generation of self-biased planar microwave devices.