Low-loss barium ferrite quasi-single-crystals for microwave application Available to Purchase

Barium hexaferrites $(BaFe12O19)$ are especially useful for microwave/millimeter devices. Due to large ferromagnetic resonance (FMR) loss (linewidths $>2kOe$⁠), traditional compacts of polycrystalline Ba ferrites indeed hinder the utilization of the materials for practical devices. The present experiment demonstrates that the quasi-single-crystal Ba ferrite disks can be fabricated by a single solid-state reaction technique without liquid phase participation, combining with a processing of alignment for the ferrite seed crystals. The ferrite bulks show a pure hexagonal Ba ferrite phase, an expected $4πMs$ of $4.48kG$⁠, and coercivity of $10∼20Oe$ along the $c$ axis, similar to the results of a typical single crystal. The FMR measurement indicates that the sample yields an anisotropy field of $16.0kOe$ and a linewidth of about $300Oe$ at $U$-band frequencies. Although the linewidth is broader than ideal Ba ferrite single crystals $(ΔH<100Oe)$⁠, it may be possible to reduce to $100Oe$ by eliminating pores, cracks, local grain boundary, and nonuniformity. In terms of material preparation, we believe that it is cost effective in the production of future microwave devices.