Regensburg 2002 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 22: Postersitzung III: Syst. korr. Elektr.: Theorie II (1-15), Metall-Isol.- und Phasenüberg
änge (16-33), SL: Massivmat., Bandl., Pinning, Vortexdyn., Transport, Korngr. (34-43), Niedrigdim. Syst., Magnetotransport (44-63)

TT 22.17: Poster

Donnerstag, 14. März 2002, 14:00–17:30, A

Structural and magnetic aspects of the metal-insulator transition in Ca_2−xSr_xRuO₄ — •O. Friedt^1,2, M. Braden², G. André¹, P. Adelmann³, S. Nakatsuji⁴, and Y. Maeno^4,5 — ¹Laboratoire Léon Brillouin, CEA/CNRS, F-91191 Gif-sur-Yvette — ²II. Physikalisches Institut, Universität zu Köln, Zülpicher Str. 77, D-50937 Köln — ³Forschungszentrum Karlsruhe, IFP, Postfach 3640, D-76021 Karlsruhe — ⁴Departement of Physics, Kyoto University, Kyoto 606-8502, Japan — ⁵CREST,Japan Science and Technology Corporation, Kawaguchi, Saitama 332-0012, Japan

We have studied the phase diagram of Ca_2−xSr_xRuO₄ over the whole region of x by neutron scattering on powder and crystalline samples. The experiments reveal antiferromagnetic order and structural distortions of the K₂NiF₄ structure type characterized by tilts and rotations of the RuO₆ octahedra. Our results strongly suggest that the structural distortions of the isovalent samples tune the magnetic as well as the electronic behaviour. In particular we observe for low Sr concentrations (x<0.2) characteristic changes of the Ru-O bonds and tilt angles which are associated with a metal-insulator transition and AFM-ordering. Further the suppression of the tilt distortion, observed for x_c≃ 0.5, is accompanied by a critical increase of low temperature susceptibility. Additionally we present the phonon dispersion and the magnetic excitations close to x_c.