Low temperature transport and specific heat studies of Nd1−xPbxMnO3 single crystals

Abstract

Journal of Physics: Condensed Matter Low temperature transport and specific heat studies of Nd1−xPbxMnO3 single crystals

N Ghosh1,4, U K Rößler2, K Nenkov2, C Hucho1, H L Bhat3 and K-H Müller2

Published 4 September 2008 • IOP Publishing Ltd Journal of Physics: Condensed Matter, Volume 20, Number 39 Download Article PDF Figures References Download PDF

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ghosh.nilotpal@gmail.com Author affiliations

1 Paul Drude Institut für Festkörperelektronik, Hausvogtei Platz 5-7, Berlin-10117, Germany

2 IFW Dresden, POB 270116, 01171 Dresden, Germany

3 Physics Department, Indian Institute of Science, C V Raman Avenue, Bangalore-560012, India

4 Author to whom any correspondence should be addressed. Present address: Institut für Experimentelle Physik II, Universität Leipzig, Linne Straße 3-5, 04103 Leipzig, Germany Dates

Received 18 April 2008 In final form 20 July 2008 Published 4 September 2008 Citation

N Ghosh et al 2008 J. Phys.: Condens. Matter 20 395219

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https://doi.org/10.1088/0953-8984/20/39/395219

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Electrical transport and specific heat properties of Nd1−xPbxMnO3 single crystals for 0.15≤x≤0.5 have been studied in the low temperature regime. The resistivity in the ferromagnetic insulating (FMI) phase for x≤0.3 has an activated character. The dependence of the activation gap Δ on doping x has been determined and the critical concentration for the zero-temperature metal–insulator transition is determined as xc≈0.33. For a metallic sample with x = 0.42, a conventional electron–electron (e–e) scattering term {\propto }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 T1/2 weak-localization contribution to resistivity for a disordered three-dimensional electron system. The specific heat data have been fitted to contributions from free electrons (γ), spin excitations (β3/2), lattice and a Schottky-like anomaly related to the rare-earth magnetism of the Nd ions. The value of γ 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.