Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 20: Correlated Electrons - Poster Session

TT 20.52: Poster

Mittwoch, 28. März 2007, 14:00–17:45, Poster A

Transport and Ordering of Polarons in PrCaMnO: Electric induced Colossal Resistance Effect — •Sebastian Schramm, Peter Moschkau, Jörg Hoffmann, and Christian Jooss — Institut für Materialphysik, Universität Göttingen

The resistivity of the low-bandwidth manganite Pr_1−xCa_xMnO₃ (x=0.3 and x=0.5) is affected by electric fields and currents. This Colossal Electroresistance (CER) includes a continuous lowering of the resistivity for high temperatures with increasing current and a sharp resistivity-drop at the characteristic temperature T_c for high currents. In thin films of PrCaMnO prepared by Pulsed Laser Deposition on SrTiO₃-substrates the resistivity in a wide temperature range can be described by a model, where thermally activated polarons (TAP) are the effective charge carriers. In a detailed series the resistivity especially of annealed samples shows a good agreement with the TAP-model. The change of resistivity in the PrCaMnO-films is a current-induced effect, strong Joule heating occurs as a secondary effect due to inherent nonlinearities in the current-voltage-characteristics. The resistivity-drop is accompanied by the destruction of a polaron-ordered phase and by a related structural modification of the lattice. The starting point of this dynamical disordering process is defined by a temperature dependent critical current and a critical electric field.