Abstract
We have fabricated a high quality magnetic Ni0.5Zn0.5Fe2O4 ferrite powder/polymer composite sheet consisting of common and environmentally friendly elements only. The sheet was then tested for its dynamic permeability by irradiating with electromagnetic waves with frequencies up to 50 GHz. Two different originally developed methods were used for the high-frequency permeability measurements, a short-circuited microstrip line method and a microstrip line-probe method. It is challenging to measure the dynamic permeability of magnetic thin films/sheets beyond 10 GHz because of the low response signal from these materials. However, the two methods produced essentially equivalent results. In the frequency dependent permeability profile, the maximum position of the profile, mu ^{prime prime }_{max}, shifted towards higher frequencies upon increasing an applied (strong) static external magnetic field, H_{dc}. A linear relationship between mu^ {prime prime }_{max} and H_{dc} for the entire range of H_{dc} was observed even at small H_{dc}. In general, the spinel-structured Ni-based ferrites exhibit low magnetic anisotropy, but the present sample showed a uniaxial-anisotropic behavior in the parallel direction of the sheet. Our Ni0.5Zn0.5Fe2O4 powder/polymer composite sheet thus exhibits high performance at GHz frequencies, and should be applicable e.g. as an anisotropic electromagnetic wave-interference material.
Highlights
We have fabricated a high quality magnetic Ni0.5Zn0.5Fe2O4 ferrite powder/polymer composite sheet consisting of common and environmentally friendly elements only
By taking into account the discussions above, we suggest that the damping of the present Ni0.5Zn0.5Fe2O4 powder/polymer composite sheet could be largely related to the 3d electrons from Fe and Ni atoms
We applied two different originally developed techniques, short-circuited MSL10,15,19 and microstrip line (MSL)-probe[11,20] methods, to a N i0.5Zn0.5Fe2O4 powder/polymer composite sheet prepared from high-quality Ni0.5Zn0.5Fe2O4 ceramic powder
Summary
We have fabricated a high quality magnetic Ni0.5Zn0.5Fe2O4 ferrite powder/polymer composite sheet consisting of common and environmentally friendly elements only. It is challenging to measure the dynamic permeability of magnetic thin films/sheets beyond 10 GHz because of the low response signal from these materials. Our Ni0.5Zn0.5Fe2O4 powder/polymer composite sheet exhibits high performance at GHz frequencies, and should be applicable e.g. as an anisotropic electromagnetic wave-interference material. For the practical use of these magnetic materials, dynamic permeability behaviors under the irradiation of high-frequency electromagnetic waves is a key issue, because permeability determines the applicable frequency bands of magnetic-based devices. The dynamic permeability of the GHz region is evaluated based on reflection or transmission methods. Wave interference (EMI) may become a serious problem In this regard, the magnetoplumbite-structured AFe12O19 ferrites[17], spinel-structured Ni1-xZnxFe2O4 ferrites, and soft magnetic alloy materials mixed with polymers[18] are expected to be attractive materials, especially in the field of EMI at GHz bands
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