Metal-insulator Transitions And Giant Magnetoresistance In Perovskite Oxides

Content Provider	Indian Institute of Science (IISc)
Author	Rao, C. N. R.
Copyright Year	1998
Abstract	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.
File Format	PDF
Journal	PeerReviewed
Language	English
Publisher	Royal Society
Publisher Date	1998-01-15
Access Restriction	Authorized
Subject Keyword	Solid State & Structural Chemistry Unit
Content Type	Text
Resource Type	Article