The tunneling magnetoresistance of Co-35(SiO2)(65) nanogranular films

A series of Co-35(SiO2)(65) (volume fraction) nanogranular films were prepa red by ion-beam sputtering at room temperature. A tunneling magnetoresistan ce (TMR) of about 4% at room temperature was observed. With applied magneti c field of about 1.5 x 10(3) Oe parallel to the plane of substrates during fabrication, the TMR ratio of the sample increased up to about 5% at room t emperature. 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 perp endicular to the plane of the sample may be due to shape-induced anisotropy . (C) 2000 American Institute of Physics. [S0021-8979(00)01007-0].