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Magnetoresistance of a (γ-Fe2O3)80Ag20 nanocomposite prepared in reverse micelles

Wiemann, Joan A.
Carpenter, Everett E.
Wiggins, Jason
Zhou, Weilie
Tang, Jinke
Li, Sichu
John, Vijay T.
Long, Gary J.
Mohan, Amitabh
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.
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University of Wyoming. Libraries