20 Gigahertz noise suppressor based on ferromagnetic nanowire arrays

The noise suppressors based on ferromagnetic nanowire arrays were fabricated on the anodic aluminum oxide templates (AAO), and the effects of the width and length of the device and the type of the ferromagnetic nanowire array on the microwave properties of the noise suppressor were investigated. The Co and Co-Ni magnetic nanowires with an average diameter of 200 nm and a length of 10 or 30 μm were electrodeposited in the AAO templates, and the ultrasonic vibration was utilized to promote ionic diffusion and to allow hydrogen to escape easily from the cathode. Scanning electron microscope images showed uniform ferromagnetic nanowires and the hysteresis loops demonstrated that these nanowire arrays had a strong magnetic anisotropy. The resonance frequency of S₂₁ of the noise suppressors reached 25 GHz, indicating that the working frequency of the devices was beyond 20 GHz. The synthetic method of the ferromagnetic nanowires and the fabrication processes of the devices in this work could be applied to other microwave devices such as isolators and circulators.