Magnetoresistance of a (γ-Fe2O3)80Ag20 nanocomposite prepared in reverse micelles
journal contributionposted on 01.05.2000, 00:00 by Joan A. Wiemann, Everett E. Carpenter, Jason Wiggins, Weilie Zhou, Jinke Tang, Sichu Li, Vijay T. John, Gary J. Long, Amitabh Mohan
The magnetic and transport properties of a (γ-Fe2O3) 80Ag20 nanocomposite, prepared by a reverse micelle technique, have been studied. γ-Fe2O3 nanoparticles and Ag particles were individually synthesized in reverse micelles. The nanocomposite material was then prepared by mixing the two different particles in a γ-Fe2O3/Ag molar ratio 80/20. The morphology of the nanoparticles was examined with transmission electron microscopy. Mössbauer spectra revealed no obvious presence of any divalent iron. Zero field cooled and field cooled magnetic susceptibilities indicated a blocking temperature of about 40 K. Negative magnetoresistance was observed resembling that in ball milled γ-Fe2O3/Ag nanocomposites. However, the magnitude of the negative magnetoresistance is smaller and is ~2.2% at 220 K and 9 T. Two possible mechanisms, spin-dependent hopping and tunneling across magnetic barriers, are discussed.