Abstract
Fe–SiO 2 granular films with various metal volume fractions ( f v) were fabricated by RF co-sputtering. The microstructure and magnetic properties as well as the tunneling magnetoresistance (TMR) were systematically investigated. The TMR exists in the samples with f v<0.5, and the Fe 0.33(SiO 2) 0.67 film exhibits the largest TMR value of −3.3% at room temperature under 1.3 T magnetic field. The transmission electron microscopy images indicate that these samples consist of small Fe particles with the size range from 1.0 to 15.0 nm separated by insulating SiO 2 matrix and exhibit TMR effect. Mössbauer measurement reveals that more superparamagnetic Fe component and less paramagnetic Fe 2SiO 4 are in favor of the higher probability of spin-dependent tunneling, thus larger TMR value. For the samples with f v⩾0.43, Mössbauer study shows the existence of perpendicular magnetic anisotropy, and the strongest perpendicular magnetic anisotropy was observed in the sample of Fe 0.47(SiO 2) 0.53. This phenomenon may be ascribed to the stress anisotropy in this film.
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