Noise suppressor by using nanogranular Co-Fe-Al-O multilayer film with different thickness

An electromagnetic noise is a serious concern at high frequencies and this is particularly true in the GHz frequency range where most of current wireless communications devices are operated. Magnetic materials have played important roles in effectively suppressing´ electromagnetic noise and the basic mechanism in this case is the loss generation of ferromagnetic resonance (FMR). In an effort to extend the noise suppression bandwidth, a double-layered structure is used consisting of two magnetic thin films separated by a non-magnetic spacer. The main idea is to vary the thickness of the double magnetic thin films, resulting in a different shape anisotropy and hence FMR frequency. A nanogranular Co-Fe-Al-O alloy is used as the magnetic thin film in both layers and SiO₂ as the spacer layer.