Giant magnetoresistance in Fe-In2O3 granular films

The magnetic properties and giant magnetoresistance effect of ferromagnetic (FM) metal-semiconductor matrix Fe-x(In2O3)(1-x) granular films prepared by the radio frequency sputtering have been investigated systematically. The magnetoresistance (MR) ratio Deltarho/rho(0) value of the granular films sample with Fe volume fraction x = 35% is 4.5% at room temperature. Temperature dependence of the MR ratio Deltap/p(0) value of Fe-0.35(In2O3)(0.65) granular films shows that Deltarho/rho(0). value below 10 K increases rapidly with the decrease of the temperature, and when T = 2 K, Deltarho/rho(0) 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 Deltarho/rho(0) 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. (C) 2002 Elsevier Science B.V. All rights reserved.