The tunneling magnetoresistance of Co35(SiO2)65 nanogranular films

A series of Co35(SiO2)65 (volume fraction) nanogranular films were prepared by ion-beam sputtering at room temperature. A tunneling magnetoresistance (TMR) of about 4% at room temperature was observed. With applied magnetic field of about 1.5×103 Oe parallel to the plane of substrates during fabrication, the TMR ratio of the sample increased up to about 5% at room temperature. The results of ferromagnetic resonance showed that the isolated Co particles embedded in the SiO2 matrix were pancake-like in shape. Thus the discrepancy of TMR between the applied magnetic field parallel and perpendicular to the plane of the sample may be due to shape-induced anisotropy.