Magnetic properties and giant magnetoresistance in Fe0.35(In2O3)0.65 granularfilm

Abstract

Fe/In2O3 granular films have been prepared by the radio frequency sputteringmethod. The magnetic and transport measurements of a representativesample, Fe0.35/(In2O3)0.65, showed that there exist different magneticstates in different temperature regions. At room temperature, the filmshows superparamagnetic behaviour, and a 5.2% magnetoresistance (MR)ratio was obtained. The susceptibility measurements showed that theblocking temperature is 50 K. Below a certain freezing temperatureTfof about 10 K, the film transits from the ferromagnetic state to theparticle-spin-cluster state. In this event, the MR ratio of the film increasesdramatically with decreasing temperature. A maximum giant magnetoresistance(GMR) ratio up to 506% is obtained at the metal–semiconductor transitiontemperature of about 2.2 K. The mechanism of this GMR is related to theinteraction with the impurities influencing the local magnetization which is quitedifferent to the spin-dependent tunnelling effect at room temperature.