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TT: Fachverband Tiefe Temperaturen

TT 79: Correlated Electrons - Poster Session

TT 79.55: Poster

Mittwoch, 2. April 2014, 15:00–19:00, P2

Large lattice distortions associated with the magnetic transition in La_0.7Sr_0.3MnO₃ — •Frank Weber¹, Dimitri Argyriou^2,3, Oleksandr Prokhnenko⁴, and Dmitry Reznik⁵ — ¹Institut für Festkörperphysik, Karlsruher Institut für Technologie, D-76021 Karlsruhe, Germany — ²European Spallation Source ESS AB, PO Box 176, SE-221 00 Lund, Sweden — ³Department of Synchrotron Radiation Research, Lund University, Box 118, Lund, Sweden — ⁴Helmholtz-Zentrum Berlin für Materialien und Energie, D-14109 Berlin, Germany — ⁵Department of Physics, University of Colorado - Boulder, Boulder, CO 80309

Colossal magnetoresistance (CMR) is associated with the phase transition from a metallic ferromagnetic to insulating paramagnetic phase, which can be controlled by an applied magnetic field. The insulating phase occurs due to trapping of the charge carriers by polaronic lattice distortions, which raise the resistivity. Theories based on local physics predict that the magnitude of the resistivity jump at T_C is determined by how much, on average, the amplitude of these distortions increases at the phase transition. Using neutron scattering, we measured the average distortion amplitude in La_0.7Sr_0.3MnO₃. Surprisingly, its increase from below to above T_C is just as large as in other manganites, which have a much larger resistivity jump. This result suggests that the strength of CMR is determined not by the size of distortions, but by their cooperative nature, specific to each compound. Existing theories need to be extended to include correlations between different unit cells to explain and predict the strength of CMR.