Nano Science and Technology InstituteNano Science and Technology Institute
Nano Science and Technology Institute 2003 NSTI Nanotechnology Conference & Trade Show
Nanotech 2003
BioNano 2003
Index of Authors
2003 Sub Sections
Press Room
NSTI Events
Site Map
Nanotech Proceedings
Nanotechnology Proceedings
Supporting Organizations
Supporting Organizations
Event Contact
696 San Ramon Valley Blvd., Ste. 423
Danville, CA 94526
Ph: (925) 353-5004
Fx: (925) 886-8461

Finite-Size Effects and Spin-Dependent Transport in Magnetite Nanoparticles

Kai Liu, L. Zhao, P. Klavins, Frank E. Osterloh, and Daniel P. Hewitt
University of California, Davis, US

Keywords: magnetite, spin-dependent tunneling, superparamagnetic, finite-size, magnetization

Nanoparticles of magnetite (Fe3O4) have been synthesized using an aqueous precipitation technique. The particles are spherical in shape, with an average size of 8-9 nm and a small size distribution, revealed by transmission electron microscopy and atomic force microscopy. A single-phase Fe3O4 cubic spinel structure and the small size of the nanoparticles are confirmed by powder x-ray diffraction. Dispersed nanoparticles displays superparamagnetic behavior above 150K over a 30s time scale. The corresponding magnetic interaction volume indicates clustering of the nanoparticles. The blocking behavior is modified by the packing density, or the average inter-particle distance, of the particle assembly. Comparing to bulk magnetite, the saturation magnetization in nanoparticles decreases faster with increasing temperatures, still according to T^3/2, due to enhanced contributions from surface magnetizations. In a compressed pellet form, the electron transport is by tunneling through adjacent particles. The resistivity increases exponentially with decreasing temperature, however, no clear evidence of a Verwey transition is observed between 110K and 300K. Negative magnetoresistance, -8.6% at 200K and ?4.5% at 300K, has been observed. This is due to the field-induced alignment of the nanoparticles magnetization directions.

NSTI Nanotech 2003 Conference Technical Program Abstract

Featured Sponsors
Nanotech Sponsors
News Headlines
NSTI Online Community

© Nano Science and Technology Institute, all rights reserved.
Terms of use | Privacy policy | Contact