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Influence of dopant concentration on the structure and physical properties of $Nd_{1-x}Pb_xMnO_3$ single crystals

Ghosh, Nilotpal and Elizabeth, Suja and Bhat, HL and Nalini, G and Muktha, B and Row, Guru TN (2005) Influence of dopant concentration on the structure and physical properties of $Nd_{1-x}Pb_xMnO_3$ single crystals. In: Journal of Solid State Chemistry, 178 (1). pp. 120-127.

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Abstract

The structure of $Nd_{1-x}Pb_xMnO_3$ crystal for x = 0.25 is determined at room temperature by single-crystal x-ray diffraction. The structural refinement reveals that the crystal is tetragonal with space group P4/mmm, Z = 4 and R of 8.3%. The lattice parameters are a = 7.7652(1) $\AA$, c = 3.884(1) $\AA$ and $\alpha = \beta = \gamma = 90^o$. The structural analysis is then extended to x = 0.38. It is noticed that substitution of Pb at the Nd site results in structural phase change from tetragonal (x = 0.25) to cubic (x = 0.38). These changes are attributed to the progressive removal of inter-octahedral tilting and minimization of the octahedral distortion leading to a higher symmetry as doping concentration increases. While the unit cell volume of tetragonal structure (P4/mmm) is comparable to that of parent $NdMnO_3$ (Pnma), the volume of cubic unit cell $(Pm \bar{3}m)$ is doubled. Electron diffraction patterns support these results and rule out the possibility of twinning. Changes in transport properties as a function of temperature at different doping levels are in accordance with the observed structural changes. It is observed that $T_{\theta}$ and $T_{MI}$ increase with x.

Item Type: Journal Article
Additional Information: The Copyright belongs to Elsevier.
Keywords: Manganites;Perovskite;Crystal structure;Superlattice; MI transition;Ferromagnetism;Ty;TMI
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Division of Physical & Mathematical Sciences > Physics
Date Deposited: 17 Mar 2006
Last Modified: 19 Sep 2010 04:24
URI: http://eprints.iisc.ernet.in/id/eprint/5820

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