Post-heat-treated spin-spray plated MnxZnyFe3−x−yO4 films exhibiting high resistivity and noise suppressing properties

Mn x Zn y Fe 3 − x − y O 4 films with a tailored microstructure were prepared by the spin-spray technique. The films were then heat treated (260°C for 3min) in a similar way to that of the reflow soldering process. The as-prepared and heat-treated films were studied for their structural, electrical, and magnetic properties. By using an oxidizing solution of CH3COONa+(NH4)2CO3+NaOH+NaNO2 (in contrast to that of CH3COONa+NaNO2 in the conventional spin spray), Mn concentration (CMn) in the film was increased and a narrow columnar structure was obtained. This structure resulted in an increased surface resistivity (ρs), thereby good noise suppressing properties even after the heat treatment. The films exhibited a high deposition rate of up to 63nm∕min with a good adhesion to the substrate. A slight decrease in the saturation magnetization (Ms) and increase in the uniaxial anisotropy field (Hk), and coercivity (Hc) were observed due to the heat treatment. The films also exhibited a decrease in imaginary permeability in the lower frequencies and the resonance frequency (fr) shifted to a higher frequency range. The film characteristics were as follows: Ms of 450–570emu∕cm3, Hc of 18–45Oe, Hk of 43–86Oe, ρs of 103–107Ω∕sq, initial permeability μ′ of 25–60, imaginary permeability μ″ of 20–38, and resonance frequency fr of 530–750MHz. The films prepared at optimum condition exhibited reflection loss (S11) less than −10dB and the transmission loss (ΔPloss) of up to 50% at 10GHz. ΔPloss exhibited uniform distribution up to 1GHz even after the heat treatment.