Regensburg 2004 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 20: Metall-Isolator-Überg
änge

TT 20.6: Vortrag

Mittwoch, 10. März 2004, 15:45–16:00, H18

Low temperature instability and magnetic entropy in La_7/8Sr_1/8MnO₃ — •Jochen Geck¹, Peter Wochner², Sven Kiele³, Rüdiger Klingeler⁴, Pascal Reutler⁴, and Bernd Büchner⁴ — ¹II. Physikalisches Institut der RWTH Aachen — ²Max-Planck-Institut für Metallforschung, Stuttgart — ³HASYLAB am DESY, Hamburg — ⁴Leibniz-Institut für Festkörper- und Werkstoffforschung, Dresden

Specific heat and magnetization measurements reveal that the entropy changes at the metal-insulator transition of La_1−xSr_xMnO₃ with x∼ 1/8 are mainly of magnetic origin. This intriguing feature necessarily implies a low temperature instability of the ferromagnetic insulating (FMI) phase in La_1−xSr_xMnO₃. Indeed, such an instability is observed: The FMI-phase decays upon x-ray irradiation at temperatures below 30 K. Moreover, the doping dependence of short range correlations above the metal-insulator transition can be consistently interpreted in terms of magnetic entropy changes.