Preparation and characterization of ZnSn-substituted barium ferrite thin films

The preparation of ZnSn-substituted barium ferrite films by sputtering deposition was studied. The as-sputtered films were amorphous, and annealing at a minimum of 750 °C was required to crystallize the films, based on the X-ray diffraction analysis and the magnetic measurements. Scanning electron microscopy combined with energy-dispersive X-ray spectroscopic microanalysis confirmed that the films were single phase with the composition BaZnxSnxFe12−2xO19, x=0.2−0.3, and their thicknesses were 0.4–1.0 μm when annealed at 750–900 °C. Atomic and magnetic force microscopy studies showed no significant grain growth upon annealing and that the films consisted of single-domain grains forming interaction-cluster-type domains. The natural ferromagnetic resonance frequency was determined at around 4 GHz, together with substantial magnetic losses that make these films promising candidates for microwave absorbers.

Research highlights
► ZnSn-substituted barium ferrite films can be prepared with a sputtering-deposition followed by annealing at 750–900 °C.
► The ZnSn-substituted barium ferrite films consist from magnetically coupled single-domain grains.
► The ZnSn-substitution in barium ferrite films reduces the ferromagnetic resonance from 48 to 4 GHz.
► The ZnSn-substituted barium ferrite films show large magnetic losses at 7–15 GHz.
► The ZnSn-substituted barium ferrite films are suitable for microwave absorbers.