37 multilayer. Figure 2

Cross-sectional scanning electron microscopy (SEM) images of FeCo/(FeCo) 0.63 (SiO2) 0.37 film. Prepared by focused ion beam sectioning polished at 30 keV (the design thickness of the FeCo layer was 10 nm, and the FeCo-SiO2layer was 20 nm). The Hysteresis loops for monolayer and multilayer films were plotted in Figure 3, and the FeCo content of both films was about 72 at %. It was observed that the multilayer films had a much lower coercivity H c about 10 Oe, while for the monolayer films, the coercivity was as high as 100 Oe. In our case, the change of the coercivity was the result of lower anisotropy field in multilayer films. Meanwhile for both films, the strait variation in the saturation magnetization Caspase inhibition which was decided by the content of magnetic phase was understandable. Figure 3 Hysteresis loops for monolayer and multilayer films. Then, contrasted to the high-frequency properties HDAC inhibitors cancer of the monolayer films (in Figure 4a) with the multilayer films (in Figure 4b), we can found that the complex permeability of the films which has multilayer structure had a huge improvement. The maximum real and imaginary parts of permeability, increasing twice higher than the monolayer films, were about 250 and 350, respectively, and a relatively wide frequency range that the imaginary part of permeability

higher than 100 was from 1.7 to 4 diglyceride GHz. However, the resonant frequency of multilayer films was decreased to 2.3 GHz simultaneously. Figure 4 The complex permeability of the films: (a) FeCo-SiO 2 monolayer, (b) FeCo/(FeCo) 0.63 (SiO 2 ) 0.37 multilayer. It is considered that for the monolayer structure FeCo-SiO2 films, almost the magnetism phase was isolated by non-magnetism phase because the FeCo particles were embedded in SiO2 matrices shown in Figure 1a. The magnetic structure of particles could be regarded as single domains due to the size of the magnetic particles smaller than the critical size of single domain which is dozens of nanometers for Fe65Co3[8]. Thus, the

magnetic moment orientation of the single domain was their respective preferred direction and chaotic in plane, and the result relative to high in-plane anisotropy field of the films would improve the resonant frequency and coercivity and reduce the permeability. Nevertheless, for the multilayer structure FeCo/(FeCo)0.63(SiO2)0.37 films, the domain orientation of individual FeCo layers was consistent owing to the applied magnetic field during sputtering. In order to certify the zero body magnetic charge and minimum magnetostatic energy, two adjacent FeCo layers presented reverse magnetic moment orientation. Meanwhile, the FeCo particles of FeCo-SiO2 layers which were similar to monolayer films could be regarded as single domain particles.