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Synthesis, structure and magnetic properties of $Ln_{1-x}A_xMnO_3$ Ln = Pr, Nd; A = Na, K from NaCl or KCl flux

Shivakumara, C and Hegde, MS and Srinivasa, T and Vasanthacharya, NY and Subbanna, GN and Lalla, NP (2001) Synthesis, structure and magnetic properties of $Ln_{1-x}A_xMnO_3$ Ln = Pr, Nd; A = Na, K from NaCl or KCl flux. In: Journal of Materials Chemistry, 11 (10). pp. 2572-2579.

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Abstract

Na- or K-substituted $PrMnO_3$ and $NdMnO_3$ phases have been prepared using neutral NaCl or KCl fluxes at a relatively low temperature of $900^o C$. These flux syntheses not only promote the reaction at low temperatures but also act as a source of the alkali metal in the final product. The structures of these oxides have been refined by the powder X-ray Rietveld method and confirmed by the electron diffraction studies. All these phases crystallize in the orthorhombic structure (space group Pbnm) and are ferromagnetic insulators. Na-doped mixed rare-earth manganites of the formula $(Pr_{1-x}La_x)_{1-y}$ $Na_yMnO_3$ $(0\leq x\leq 0.80; 0.08\leq y\leq 0.15)$ have also been synthesized in NaCl flux; among these mixed rare-earth manganites those crystallizing in rhombohedral structures are ferromagnetic metals (FMM), and those in orthorhombic structures are ferromagnetic insulators (FMI). The phase diagram of average A-site radii vs. ferromagnetic transition temperature, Tc, of the stoichiometric phases has been constructed here and compositions with $<r_A> \leq 1.20 \AA$ crystallizing in the orthorhombic structures fall in the ferromagnetic insulating region. Compositions with $<r_A> \geq 1.20 \AA$ crystallize in the rhombohedral structures and these are ferromagnetic metals.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Royal Society of Chemistry.
Department/Centre: Division of Chemical Sciences > Materials Research Centre
Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 16 Oct 2008 09:19
Last Modified: 19 Sep 2010 04:49
URI: http://eprints.iisc.ernet.in/id/eprint/15897

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