Transverse resistance measurements: a very sensitive probe to charge inhomogeneities in manganites

Abstract

Transverse resistance measurements are reported on patterned epitaxial thin films of optimally doped La2/3Ca1/3MnO3 oxides. We show that the voltage drop measured across a micron-size patterned track displays a temperature dependence that, particularly in a temperature region around the Curie temperature, cannot be explained solely by the contribution of a longitudinal resistivity component. We argue that this response reflects inhomogeneous current flow, which sets in dramatically around the Curie temperature, likely related to charge trapping at microstructural defects. Indeed, we show that appropriate thermal annealing allows reducing to some extent their contribution. Thus we conclude that this experimental set-up allows for the monitoring of how electronic phase separation develops in optimally doped manganites. The impact of this effect on the determination of Hall coefficients is discussed.