Negative magnetoresistance of γ-Fe2O3 observed in γ-Fe2O3/Ag granular nanocomposites
The magnetoresistance of (γ-Fe2O3)xAg100-x (x=50–90), a granular system where insulating magnetic nanoparticles and nonmagnetic metal are intimately mixed, has been studied at room temperature. For high silver concentration (x≤70), samples are metallic and exhibit ordinary positive magnetoresistance. Below the percolation threshold, which is 11.4 vol% of silver (x=71), samples are insulators. Our data suggest that direct tunneling between silver grains across γ-Fe2O3 barriers dominates at low temperature and variable range hopping becomes the main transport mechanism at high temperature. The ...
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