# Low temperature transport and specific heat studies of $Nd_{1-x}Pb_xMnO_3$ single crystals

Ghosh, N and R¨oßler, UK and Nenkov, K and Hucho, C and Bhat, HL and M¨uller, KH (2008) Low temperature transport and specific heat studies of $Nd_{1-x}Pb_xMnO_3$ single crystals. In: Journal of Physics-Condensed Matter, 20 (39). pp. 395219-1.

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## Abstract

Electrical transport and specific heat properties of $Nd_{1-x}Pb_xMnO_3$ single crystals for $0.15\leq x \leq 0.5$ have been studied in the low temperature regime. The resistivity in the ferromagnetic insulating (FMI) phase for $x \leq 0.3$ has an activated character. The dependence of the activation gap \Delta on doping x has been determined and the critical concentration for the zero-temperature metal-insulator transition is determined as $x_c \approx 0.33$. For a metallic sample with x = 0.42, a conventional electron-electron (e-e) scattering term $\alpha T^2$ is found in the low temperature electrical resistivity, although the Kadowaki-Woods ratio is found to be much larger for this manganite than for a normal metal. There is a resistivity minimum observed around 60 K for a metallic sample with x = 0.5. The effect is attributed to weak localization and can be described by a negative $T^{1/2}$ weak-localization contribution to resistivity for a disordered three-dimensional electron system. The specific heat data have been fitted to contributions from free electrons (\gamma), spin excitations $(\beta_{3/2})$, lattice and a Schottky-like anomaly related to the rare-earth magnetism of the Nd ions. The value of \gamma is larger than for normal metals, which is ascribed to magnetic ordering effects involving Nd. Also, the Schottky-like anomaly appears broadened and weakened suggesting inhomogeneous molecular fields at the Nd-sites.

Item Type: Journal Article Copyright of this article belongs to Institute of Physics. Division of Physical & Mathematical Sciences > Physics 20 Oct 2008 05:35 19 Sep 2010 04:51 http://eprints.iisc.ernet.in/id/eprint/16173