Self-biased nanocrystalline barium hexaferrite thick films formed by aerosol deposition for microwave devices

High-frequency devices utilizing magnetic materials such as barium hexaferrite (BaFe₁₂O₁₉, BaM) are critical for many electronics. One promising route to forming these materials is aerosol deposition (AD), a process that creates thick 95% dense films by room-temperature impact consolidation^*. AD utilizes high-velocity impact to fracture and mechanically and chemically bonds solid particles together.
We use AD to deposit BaM in a non-magnetically biased (NMB) and in a 4 kOe bias field (MB). We report results of these films as-deposited and sintered from 700C to 1000C.

The best films were deposited under MB and annealed at 1000C and show a clear OOP orientation (23 % improvement compared to NMB). Properties include, magnetic saturation: 62 emu/g (72 emu/g bulk) and remanence: 43 emu/g. FMR results give an anisotropy field of 15 kOe (16 kOe bulk), linewidth of 1.8 kOe, and damping factor of 4x10^-4. Films deposited under NMB show comparably poorer values. XRD results suggest good crystallinity and phase uniformity overall. Sintering increases the crystallite size from about 10 nm to 25 nm.

The overall results suggest that depositing the films with AD under MB significantly increases the magnetic orientation of the film.

* S. D. Johnson et al., Mat. Research Bulletin 76 (2015) 365.