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Journal of Nanomaterials
Volume 2014 (2014), Article ID 902968, 9 pages
http://dx.doi.org/10.1155/2014/902968
Research Article

Synthesis and Magnetic Properties of Hematite Particles in a “Nanomedusa” Morphology

1Division of Materials Science, Korea Basic Science Institute, Daejeon 305-333, Republic of Korea
2Faculty of Mathematics and Physics, J. Stefan Institute and University of Ljubljana, Jamova 39, SI-1000 Ljubljana, Slovenia
3Department of Physics, Faculty of Science, University of Zagreb, Bijenička 32, 10000 Zagreb, Croatia
4Institute of Molecular Physics, Polish Academy of Sciences, Smoluchowskiego 17, 60-179 Poznań, Poland
5Faculty of Civil and Geodetic Engineering, Institute of Mathematics, Physics and Mechanics and University of Ljubljana, Jamova 2, SI-1000 Ljubljana, Slovenia
6Faculty of Chemistry and Chemical Technology, University of Ljubljana, Aškerčeva 5, SI-1000 Ljubljana, Slovenia

Received 22 August 2014; Revised 10 November 2014; Accepted 10 November 2014; Published 20 November 2014

Academic Editor: Vladimir Sivakov

Copyright © 2014 Jin Bae Lee et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

We present the synthesis, characterization, and magnetic properties of hematite particles in a peculiar “nanomedusa” morphology. The particles were prepared from an iron-silica complex by a hydrothermal process in a solution consisting of ethyl acetate and ethanol. The particles’ morphology, structure, and chemical composition were investigated by transmission electron microscopy, powder X-ray diffraction, and scanning electron microscope equipped with an energy-dispersive X-ray spectrometer. The “hairy” particles consist of a spherical-like core of about 100 nm diameter and fibrous exterior composed of thin “legs” of 5 nm diameter grown along one preferential direction. The particles’ cores are crystalline and undergo a magnetic phase transition to a weakly ferromagnetic state at a temperature of 930 K that matches reasonably the Néel temperature of bulk hematite. However, unlike bulk hematite that undergoes Morin transition to an antiferromagnetic state around room temperature and small hematite nanoparticles that are superparamagnetic, the “nanomedusa” particles remain weakly ferromagnetic down to the lowest investigated temperature of 2 K. Each particle thus represents a nanodimensional “hairy” ferromagnet in a very broad temperature interval, extending much above the room temperature. Such high-temperature ferromagnetic nanoparticles are not frequently found among the nanomaterials.