Strain induced anomalous red shift in mesoscopic iron oxide prepared by a novel technique |
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Authors: | T N Narayanan D Sakthi Kumar Yasuhiko Yoshida M R Anantharaman |
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Affiliation: | (1) Department of Physics, Cochin University of Science and Technology, Cochin, 682 022, India;(2) Bio-Nano Electronics Research Centre, Department of Applied Chemistry, Toyo University, Toyo, Japan |
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Abstract: | Nano magnetic oxides are promising candidates for high density magnetic storage and other applications. Nonspherical mesoscopic
iron oxide particles are also candidate materials for studying the shape, size and strain induced modifications of various
physical properties viz. optical, magnetic and structural. Spherical and nonspherical iron oxides having an aspect ratio,
∼2, are synthesized by employing starch and ethylene glycol and starch and water, respectively by a novel technique. Their
optical, structural, thermal and magnetic properties are evaluated. A red shift of 0·24 eV is observed in the case of nonspherical
particles when compared to spherical ones. The red shift is attributed to strain induced changes in internal pressure inside
the elongated iron oxide particles. Pressure induced effects are due to the increased overlap of wave functions. Magnetic
measurements reveal that particles are superparamagnetic. The marked increase in coercivity in the case of elongated particles
is a clear evidence for shape induced anisotropy. The decreased specific saturation magnetization of the samples is explained
on the basis of weight percentage of starch, a nonmagnetic component and is verified by TGA and FTIR studies. This technique
can be modified for tailoring the aspect ratio and these particles are promising candidates for drug delivery and contrast
enhancement agents in magnetic resonance imaging. |
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Keywords: | Nano magnetic oxides red shift magnetic storage |
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