Characterization of Micro-Structured Ferrite Materials: Coarse and Fine Barium, and Photoresist Composites

Coarse and fine anisotropic hexagonal barium ferrite (BaFe₁₂O₁₉) powders and their composites with photoresist were prepared and characterized for high frequency microelectronic applications. Partially filled rectangular microwave ferrite structures were printed on silicon wafer by spin-casting technique from the negative photo resist composites. A scanning electron microscope (SEM) was employed to characterize the surface morphology of the coarse and fine barium ferrite powders. Quasi-optical millimeter wave spectroscopy was used to measure the transmittance spectra of the ferrites and their photoresist composites in millimeter wave frequency range from 35 GHz to 75 GHz. The ferromagnetic resonance and absorption of powders and photoresist composites are investigated. Fine barium powder exhibits lower ferromagnetic resonant frequency than coarse barium powder due to the smaller particle size. But the photoresist composite of the fine barium shows same ferromagnetic resonance as the coarse powder photoresist composite.