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

• Published in: Journal of physics. Condensed matter Vol. 20; no. 39; pp. 395219 - 395219 (9)
• Main Authors: Ghosh, N, Rößler, U K, Nenkov, K, Hucho, C, Bhat, H L, Müller, K-H
• Format: Journal Article
• Language: English
• Published: Bristol IOP Publishing 01.10.2008; Institute of Physics
• Subjects: Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Magnetic properties and materials; Magnetotransport phenomena, materials for magnetotransport; Manganites; Physics; Specific heat; Schottky anomalies; Monocrystals; Electrical conductivity; Magnetic ordering; Metal-insulator transition; Chemical composition; Free electron; Ferromagnetism; Electron-electron interactions; Weak localisation; Manganites
• ISSN: 0953-8984; 1361-648X
• DOI: 10.1088/0953-8984/20/39/395219

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 Delta on doping x has been determined and the critical concentration for the zero-temperature metal-insulator transition is determined as xc0.33. For a metallic sample with x = 0.42, a conventional electron-electron (e-e) scattering term 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 (gamma), spin excitations (beta3/2), 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.