Magnetic properties and tunneling magnetoresistance in FeCo-SiO2 granular films

Fe-fv(SiO2)(1-fv) granular films were fabricated by rf sputtering (f(v) represents the Fe volume fraction). The microstructure, magnetic properties as well as the tunneling magnetoresistance effect (TMR) were systematically studied. It was found that the maximum TMR ratio is about -3.3% at f(v) = 0.33. Under the same condition, a series of (Fe100-x Co-x)(0.33)(SiO2)(0.67) were prepared. TMR value reaches -4.5% at x = 53, while the microstructure of the film still keeps as that of Fe-0.33(SiO2)(0.67). The higher TMR ratio is contributed to the elevating of the spin polarization of particles. This is consistent with Inoue's theory.