Noise suppression effect of nanogranular Co based magnetic thin films at gigahertz frequency

Noise suppression effect of Co-Pd-Al-O nanogranular thin films, which have considerably high permeability up to gigahertz range, was investigated. The films with large variety of electrical resistivity (/spl rho/) from 10/sup 2/ to 10/sup 7/ /spl mu//spl Omega//spl middot/cm were prepared by reactive sputtering method and by changing both target compositions and deposition conditions. The films with /spl rho/ less than 10/sup 3/ /spl mu//spl Omega//spl middot/cm are ferromagnetic, and the films with /spl rho/ more than 10/sup 6/ /spl mu//spl Omega//spl middot/cm are superparamagnetic. A microstrip line with granular films placed on its top was used to evaluate conduction noise suppression. The result of transmission and reflection measurements reveals that these nanogranular soft magnetic Co-Pd-Al-O thin films have high potential for noise suppressors in the gigahertz range. In particular, the broad maximum of power loss (P/sub loss//P/sub in/) about 0.6 at 6 GHz has been obtained in Co-Pd-Al-O films with /spl rho/ around 10/sup 4/ /spl mu//spl Omega//spl middot/cm.