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ASn-substituted BaM-hexaferrites with compositions BaFe12-2xAxSnxO19, where A = Co, Ni, Zn, and x = 0.5-2, were synthesized using a solid-state reaction at 1100-1300 °C. Hexaferrites formation was controlled by X-ray powder diffraction. The static magnetic properties were determined and the ferromagnetic resonance frequency of the powders was obtained using a vector network analyzer and a coplanar waveguide. It is shown that the degree of substitution (x) has a strong influence both on the static magnetic and the microwave behavior of the ceramics. Due to the changes in the anisotropy and saturation magnetization, the ferromagnetic resonance frequency shows a considerable decrease, from the 48 GHz for pure BaFe12O19, to about 10-20 GHz for samples with x ≈ 0.5, 1. [ABSTRACT FROM AUTHOR]

We have analyzed the microwave behavior of soft nanogranular (Fe0.7Co0.3)71B22Ni7 films which present a dc permeability from 60 to 280, a resistivity of 8 to 9 10-7 Ω m and a zero-field double ferromagnetic resonance peak at frequencies ranging from 3.8 to 8.35 GHz. The high frequency and large line-width of the observed resonances allows for possible applications in microwave absorbers in a frequency range extending from 6 to 10 GHz. [ABSTRACT FROM AUTHOR]

We have investigated the microwave properties of a set of Co-Fe-Al-O films with different thicknesses. The films show a well-defined in-plane anisotropy due to the bias field applied during deposition. The resonance frequency is determined through the scattering parameters measured with a vector network analyzer and a probing station connected to a coplanar waveguide. The results show that the resonance peak features depend on the direction of the applied/RF field and on the applied field history. [ABSTRACT FROM AUTHOR]