At room temperature, polycrystalline Fe3O4 films with thickness in the range 5-1120 nm have been prepared by reactive sputtering. Transmission electron microscopy imaging shows that uniform Fe3O4 grains are well separated by grain boundaries and their size decreases with film thickness. The change of resistivity as a function of temperature reveals a grain boundary dominated electron tunnelling mechanism. The magnetoresistance MR = (ρH - ρ0)/ρ0 measured at room temperature for the films thicker than 200 nm is ∼-7.4% under a magnetic field of 46 kOe, which is among the largest values ever reported for Fe3O4 films under the same measuring conditions. As the thickness reduces from 80 to 5 nm, MR decreases from -6.5% to -1.1% due to the enhanced spin-flip scattering at film and grain surfaces.
ASJC Scopus subject areas
- Electronic, Optical and Magnetic Materials
- Condensed Matter Physics
- Acoustics and Ultrasonics
- Surfaces, Coatings and Films