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Giant magnetoresistance, charge ordering and other novel properties of perovskite manganates

Rao, CNR and Mahesh, R and Raychaudhuri, AK and Mahendiran, R (1998) Giant magnetoresistance, charge ordering and other novel properties of perovskite manganates. In: Journal of the Physics and Chemistry of Solids, 59 (4). pp. 487-502.

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Giant magnetoresistance (GMR) and related properties of manganate perovskites of the general formula $Ln_{1-x}A_xMn0_3$ (Ln = rare earth; A = divalent ion) are discussed in detail. There is a fine interplay of magnetic exchange, structural properties and electronic transport in these materials which gives rise to several novel properties. The manganates am ferromagnetic at or above a certain value ofx (or $Mn^{4+}$ content) and become metallic at temperatures below the curie temperature. $T_c$. This behavior is attributed to double-exchange. GMR is generally a maximum close to $T_c$ or the insulator-metal (I-M) transition temperature, $T_{im}$. The $T_c$ and %MR are markedly affected by the size of the A site cation, $< r_A >$ , thereby affording a useful electronic phase diagram when $T_c$ or $T_{im}$ is plotted against $< r_A >$ or pressure. The commonalities and correlations found in the properties of manganates are examined along with certain unusual features in the electron-transport properties of these materials. Some of the $Ln_{1-x}A_xMnO_3$ compositions exhibit charge-ordering and related effects. Charge ordering is crucially dependent on $< r_A >$ or the er band width and the charge-ordered insulating state transforms to a metallic ferromagnetic state on the application of a magnetic field, charge-ordering and double-exchange being competing interactions.

Item Type: Journal Article
Publication: Journal of the Physics and Chemistry of Solids
Publisher: Elsevier
Additional Information: Copyright of this article belongs to Elsevier.
Keywords: D. electrical properties;D. magnetic properties
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 27 Nov 2006
Last Modified: 19 Sep 2010 04:32
URI: http://eprints.iisc.ac.in/id/eprint/8984

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