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Red Shift in Optical Absorption Tail and Superparamagnetism of γ- Fe2O3 Nanoparticles in a Polymer Matrix

Published online by Cambridge University Press:  11 February 2011

John K. Vassiliou ,
Jens W. Otto ,
V. Mehrotra  and
J. J. Davis
John K. Vassiliou
Affiliation:
Department of Physics, Villanova University, Villanova, PA 19085
Jens W. Otto
Affiliation:
Joint Research Center for the European Commission, B-1049 Brussels, Belgium
V. Mehrotra
Affiliation:
RSC Rockwell, Thousand Oaks, CA
J. J. Davis
Affiliation:
Department of Physics, Villanova University, Villanova, PA 19085
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Abstract

Well defined spherical particles of γ- Fe2O3 have been synthesized in the pores of a polymer matrix in the form of beads by an ion exchange and precipitation reaction. The particle size distribution is a gaussian with an average diameter of 80 A. The DC magnetic susceptibility and the magnetization of the nanocomposite has been measured between 4 and 300 K using a Faraday balance and a magnetometer, respectively. The magnetic measurements demonstrate that the particles are superparamagnetic with a blocking temperature Tb about 55 K. The optical absorption edge of the mesoscopic system is red shifted with respect to single crystal films of γ-Fe2O3 with an absorption tail extended deeply in the gap. Although lattice distortion and existence of excitonic states in the gap can explain the absorption behavior, the red shift can successfully be explained by the quantum confinement of an electron-hole pair in a spherical well.

Type
Research Article
Information
MRS Online Proceedings Library (OPL) , Volume 740: Symposium I – Nanomaterials for Structural Applications , 2002 , I9.4
Copyright
Copyright © Materials Research Society 2003

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