Siwach, P. K. and Srivastava, Pankaj and Singh, Jai and Singh, H. K. and Srivastava, O.N. (2009) Broad temperature range low field magnetoresistance in La0.7Ca0.3MnO3:nano-ZnO composites. Journal of Alloys and Compounds, 481 (1-2). pp. 17-21. ISSN 0925-8388

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Abstract

We report the enhanced low field magnetoresistance in broad temperature range (∼70 K) in LCMO:(%x) nano-ZnO (%x = 0, 1, 3, 5, 7 and 10) composites. Nano-ZnO has been synthesized by vapor phase transport technique which then admixed with sol–gel synthesized nano-LCMO that leads to LCMO:nano-ZnO composites. Nano-ZnO admixing does not show any significant change in lattice parameter of the composites. All samples exhibits characteristic insulator–metal (TIM) and para-ferromagnetic (TC) transition temperature, which decreases with increase in nano-ZnO content. Higher nano-ZnO (x ≥ 3%) leads to dual I–M as well as PM–FM transitions. The first transition occurs close to TIM or TC of pure LCMO and another at a significant lower temperature. At x > 7%, the double transitions transforms into a single-broad transition and at then finally disappears for x > 10%. The occurrence of dual transition has been explained on the basis of stress induced phase separation due to nanoglobular ZnO structures that result in formation of intragranular and intergranular regions having different transition temperatures. The interesting and important result for the present LCMO:nano-ZnO composites is the observation of improved MR ∼13–18% at a moderate magnetic field of 3 and 5 kG in a broad temperature range of ∼70 K (80–150 K). The improved broad range low field magnetoresistance (LFMR) has been explained on the basis of grain boundary tailoring due to coating of polar nature nano-ZnO on the LCMO grains.

Item Type:	Article
Additional Information:	Copyright for this article belongs to M/s Elsevier B.V.
Uncontrolled Keywords:	Nanostructures; Grain boundaries; Electronic transport
Subjects:	Chemistry Materials Science Metallurgy & Metallurgical Engineering
Divisions:	UNSPECIFIED
Depositing User:	Ms Neetu Chandra
Date Deposited:	14 Aug 2012 07:27
Last Modified:	14 Aug 2012 07:27
URI:	http://npl.csircentral.net/id/eprint/409

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