Effect of multilayer structure on high-frequency properties of FeCo/(FeCo) 0.63 (SiO2) 0.37 nanogranular films on flexib
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NANO EXPRESS
Open Access
Effect of multilayer structure on high-frequency properties of FeCo/(FeCo)0.63(SiO2)0.37 nanogranular films on flexible substrates Li Zhang1,2*, Sen Qin1,2, Xing Wang2, Jianliang Xie1,2 and Longjiang Deng1,2
Abstract The high-frequency properties of the FeCo-SiO2 monolayer nanogranular films and FeCo/(FeCo)0.63(SiO2)0.37 multilayer nanogranular films which were elaborated on flexible substrates by magnetron sputtering system were studied. Compared to the monolayer films with the same FeCo content, the multilayer structures comprised of FeCo/(FeCo)0.63(SiO2)0.37 exhibit more excellent properties that the real and imaginary parts of permeability, more than the double value of the monolayer, increase to 250 and 350, respectively. The variation was considered owing to the reduction of the anisotropy field. Keywords: Multilayer film, High-frequency property, Flexible substrate, Anisotropy field
Background With the rapid increase of demand for the devices used in microwave band, ferromagnetic thin films with the potential for excellent magnetic property in the GHz range, owing to their special structure characteristics and free from Snoek limitation, have been widely studied in recent years. The basic requirements for magnetic films operated in high frequency are high permeability (μ) and high resistivity (ρ) in GHz range, and metal insulating films, especially Fe and Co based films, have enormous potential to achieve a high permeability, owing to their high saturation magnetization and suitable anisotropic field [1-3]. For the monolayer ferromagnetic films, it is promising to achieve high microwave permeability to increase film thickness. However, the negative influence, the serious skin effect and eddy current [4,5], and the obvious outof-plane anisotropy in the high frequency, will block the increasing of the permeability, while the thin magnetic films, with specific multilayer structure design, can efficiently avoid the above negative effect and improve high-frequency properties by leading into different * Correspondence: [email protected] 1 Engineering Research Center of Electromagnetic Wave Absorbing Materials, Ministry of Education, Chengdu 610054, China 2 State Key Laboratory of Electronic Thin Films and Integrated Devices, University of Electronic Science and Technology of China, Chengdu 610054, China
dielectric layers [6]. In this study, FeCo-SiO2 monolayer films and FeCo/(FeCo)0.63(SiO2)0.37 multilayer films were prepared by co-sputtering and tandem sputtering on flexible substrates, respectively, and in order to discuss the improvement of multilayer films, the high-frequency properties of both films whose FeCo content was about 72 at % were investigated.
Methods FeCo-SiO2 monolayer films and FeCo/(FeCo)0.63(SiO2)0.37 multilayer films were all elaborated on flexible substrates by magnetron sputtering system under external bias magnetic field. The flexible substrates of this experiment were 13-μm thick polyethylene terephthalate films. A RF magnetron system was used to sputte
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