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TT: Tiefe Temperaturen

TT 12: Correlated Electrons - Spin Systems and Itinerant Magnets: Experiment

TT 12.2: Vortrag

Samstag, 5. März 2005, 11:00–11:15, TU H2053

Observation of a Griffiths phase in paramagnetic La_1−xSr_xMnO₃ — •Joachim Deisenhofer¹, D. Braak², H.A. Krug von Nidda¹, J. Hemberger¹, R.M. Eremina³, V.A. Ivanshin⁴, A.M. Balbashov⁵, A. Loidl¹, T. Kimura⁶, and Y. Tokura⁶ — ¹EP V, Center for Electronic Correlation and Magnetism, University of Augsburg, 86135 Augsburg, Germany — ²TP II, Institute for Physics, University of Augsburg, 86135 Augsburg, Germany — ³E.K. Zavoisky Physical-Technical Institute, 420029 Kazan, Russia — ⁴Kazan State University, 420008 Kazan, Russia — ⁵Moscow Power Engineering Institute, 105835 Moscow, Russia — ⁶Department of Applied Physics, University of Tokyo, Tokyo 113-8656, Japan

We report on the discovery of a new phase boundary above magnetic ordering in low doped La_1−xSr_xMnO₃ by means of ESR and susceptibility measurements. The observed triangular phase regime in the paramagnetic state is identified as a realization of a Griffiths phase, where disorder in the ferromagnetic bonds leads to the existence of a temperature scale above T_C. The influence of quenched disorder to allow for the occurrence of a Griffiths phase becomes evident by its appearance within the Jahn-Teller distorted orthorhombic structure.