Electrical properties of nanocrystalline magnetite with large non-stoichiometry, near Verwey transition |
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Authors: | P Brahma D Dutta A Ghosh |
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Institution: | a Gurudas College, Kolkata 700 054, India b Rammohan College, 102/1 Raja Rammohan Roy Sarani, Kolkata 700 009, India c Department of Solid State Physics, Indian Association for the Cultivation of Science, Kolkata 700 032, India d Department of Physics, University of Calcutta, Kolkata 700009, India e DST Unit on Nano Science, Indian Association for the Cultivation of Science, Kolkata 700 032, India |
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Abstract: | DC electrical measurements were carried out on compacted powders of magnetite with an average particle diameter of 50 nm over the temperature range 10-300 K. The non-stoichiometry was estimated from Mossbauer spectroscopy analysis. High-resolution X-ray diffraction studies in the temperature range 93-300 K did not show any phase transition. There was a drastic change in resistivity around 80 K but no discontinuity thereof. Electrical resistivity vs. temperature data were analysed on the basis of Mott's small polaron and variable-range hopping models, respectively. The Verwey temperature as estimated from this analysis was 93 K. From voltage-current characteristics it was concluded that there was a small intrinsic gap at the Fermi level above the transition temperature and the same increased drastically below the transition temperature. This was ascribed to a transition from short-range order to long-range order as the temperature was lowered. |
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Keywords: | Magnetite Nanoparticle Electrical properties |
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