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Metal-insulator transitions and giant magnetoresistance in perovskite oxides

Rao, CNR (1998) Metal-insulator transitions and giant magnetoresistance in perovskite oxides. In: Philosophical Transactions of The Royal Society of London Series A Matemetical Physical and Engineering Sciences, 356 (1735). pp. 23-38.

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Transition-metal oxides of perovskite structure exhibit compositionally controlled metal-insulator (M-I) transitions wherein the temperature coefficient of resistivity changes sign at a resistivity value close to Mott's maximum metallic resistivity. These oxides also obey the Mott criterion, eta(c)(1/3)a(H) approximate to 0.25, arising from electron interactions. Cuprate superconductors, in spite of their anomalous properties in the metallic state, obey the above two criteria for metallicity. The cuprates also exhibit unusual insulator-superconductor and M-I transitions. Perovskite manganates which exhibit giant magnetoresistance, on the other hand, show high resistivities (rho > rho(max) of Mott) at low temperatures, in the 'metallic' state, and the mechanism of the M-I transition in these materials is not clear. Jahn-Teller distortion and charge ordering compete with double exchange and the electronic properties are accordingly determined by the dominant interaction. While double exchange favours ferromagnetism and metallicity, charge-ordering and Jahn-Teller effects favour insulating behaviour. Charge ordering in the manganates is specially interesting being strongly affected by the size of the A-site cations.

Item Type: Journal Article
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Additional Information: Copyright of this article belongs to Royal Society.
Keywords: perovskite oxides;cuprate superconductors;giant magnetoresistance;rare earth manganates;charge ordering;spin ordering.
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 24 Dec 2009 07:40
Last Modified: 19 Sep 2010 05:25
URI: http://eprints.iisc.ernet.in/id/eprint/18915

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