Abstract
Polycrystalline Ag x (Fe 3O 4) 1− x films ( x = 0 , 0.1, 0.2 and 0.3) have been prepared by the sol–gel method in combination of the spin-coating technique with a precursor solution containing polyvinyl alcohol (PVA) on fused quartz substrates. XRD analysis and SEM images indicate that the Fe 3O 4 grains are nearly spherical single-domain particles. The coercivities of the films are about 290 Oe for x = 0.1 and 360 Oe for x = 0.3 , respectively, which are nearly the same as the magnetocrystalline anisotropic effective field H K of Fe 3O 4. At 300 K, the x = 0.1 film has a maximal magnetoresistance of −8.7% at a magnetic field of 50 kOe and −3.5% at 8.8 kOe, while the pure Fe 3O 4 film is only −2.2% at 8.8 kOe. This enhancement of the MR can be attributed to the contribution from the spin-dependent scattering at the Ag–Fe 3O 4 interfaces as well as the spin-polarized tunneling at boundaries of Fe 3O 4 grains of the spin-polarized electrons. In addition, different MR behaviors for Ag-added Fe 3O 4 bulk polycrystalline samples and polycrystalline films are discussed.
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