Giant magnetoresistance in Fe-In₂O₃ granular films

The magnetic properties and giant magnetoresistance effect of ferromagnetic (FM) metal-semiconductor matrix Fe_x(In ₂O₃)_1-x granular films prepared by the radio frequency sputtering have been investigated systematically. The magnetoresistance (MR) ratio Δρ/ρ₀ value of the granular films sample with Fe volume fraction x = 35% is 4.5% at room temperature. Temperature dependence of the MR ratio Δρ/ρ ₀ value of Fe_0.35(In₂O₃) _0.65 granular films shows that Δρ/ρ₀ value below 10 K increases rapidly with the decrease of the temperature, and when T = 2 K, Δρ/ρ₀ value is 85%. Through the study of the dependence of low field susceptibility on temperature and the hysteresis loops at different temperatures, it has been found that, when the temperature decreases to a critical point T_P = 10 K, the change of the structure in Fe_0.35(In₂O₃)_0.65 granular films results in the transformation of state from FM to magnetic disordered. The remarkable increase of the MR ratio Δρ/ρ₀ value of Fe_0.35(In₂O₃)_0.65 granular films below 10 K seems to arise from the peculiar conducting mechanism of the granular films sample in magnetic disordered state.