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Study of Superparamagnetic Relaxation in Nanophase Maghemite

Simon T. F. Hale and Rama Balasubramanian*

Department of Physics, James Madison University,
Harrisonburg, VA 22807 USA

This is an abstract for a presentation given at the
10th Foresight Conference on Molecular Nanotechnology


Maghemite is a ferromagnetic iron oxide crystal that has many applications in the magnetic recording media. It is an important magnetic oxide used to coat cassettes and floppy disks. Nanophase maghemite, often found in the corrosion coatings of atmospherically exposed structural steels, has particle size of the order of 10-20 nm and exhibit superparamagnetic behavior. In order to characterize the superparamagnetic behavior of maghemite, and to estimate the anisotropy constant as a function of particle volume, synthetic nano-crystals of Maghemite of different particle sizes were produced. The crystals were precipitated from an aqueous solution of FeCl3-FeCl2 by varying the pH level of the solution under a controlled oxidization rate. Mösssbauer spectroscopy, x-ray diffraction, and IR spectroscopy were utilized to examine the crystals size, structure, and magnetic properties of nanophase maghemite. Both x-ray diffraction and room temperature Mössbauer measurements indicated the poor crystallinity of the samples. The mean hyperfine field measured at room temperature decreased as the crystallite size was reduced. Detailed spectroscopic results on the magnetic and crystalline properties of nanophase maghemite will be presented.

Abstract in Microsoft Word® format 20,294 bytes

*Corresponding Address:
Rama Balasubramanian
Department of Physics, James Madison University
112, Miller Hall, Grace Street, Harrisonburg, VA 22807 USA
Phone: 540-568-3898 Fax: 540-568-2800


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