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TT: Tiefe Temperaturen

TT 25: Postersitzung III: Pinning und Vortexdynamik, Massive HTSL, Bandleiter, Transporteigenschaften in HTSL, SL dünner Filme, Elektronen und Phononen in HTSL, Tunneln, Borkarbide, Quantenphasen und Metall-Isolator-Überg
änge, Anwendungen, Sonstiges

TT 25.56: Poster

Thursday, March 29, 2001, 14:30–17:00, Rang S\ 3

Raman Scattering in Nd_1−xSr_xMnO₃ Single Crystals (x=0.3, 0.5) — •K.Y. Choi¹, P. Lemmens¹, G. Güntherodt¹, G. Balankrishnan², and G. Rangarajan³ — ¹2. Physikalisches Institut, RWTH Aachen, Aachen,Germany — ²Dept. of Physics, Univ. of Warwick, Coventry, U.K. — ³Dept. of Physics, IIT, Chennai, India

We report temperature- and doping-dependent Raman scattering spectra of Nd_1−xSr_xMnO₃ single crystals (x=0.3, 0.5). For x=0.3 it was found that the electronic Raman scattering in B_1g symmetry shows near a change from a diffusive response in the paramagnetic insulator phase to a flat continuum response in the ferromagnetic metallic phase. This electronic scattering intensity increases with decreasing temperature below the metal-insulator transition near T_C ∼ 235 K. This is ascribed to an increase in the density of states at the Fermi energy and an enhancement of the electronic correlations in the ferromagnetic metallic phase.
For x=0.5 the phononic Raman spectra exhibit additional modes at 489cm⁻¹, 610cm⁻¹ and 654cm⁻¹ for temperatures below T*∼ 180 K. The intensity of these modes does not fall off linearly upon approaching T*. This critical temperature is identified as the charge ordering temperature,T*≅T_CO.
Work supported by DFG/SPP1073