Regensburg 2007 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 14: Spin Systems and Itinerant Magnets

TT 14.14: Vortrag

Dienstag, 27. März 2007, 18:00–18:15, H19

Magnetism in single-layered Ruthenates — •Paul Steffens¹, Olaf Schumann¹, Yvan Sidis², Peter Link³, Satoru Nakatsuji⁴, and Markus Braden¹ — ¹II. Physikalisches Institut, Universität Köln, 50937 Köln — ²Laboratoire Léon Brillouin, Gif-sur-Yvette, France — ³FRM II, Technische Universität München, 85747 Garching — ⁴Institute of Solid State Physics, Tokyo, Japan

We present recent results on the magnetism in the single-layered ruthenates Ca_2−xSr_xRuO₄. Depending on the Sr-content x, very different properties are observed. In this contribution we focus on the region 0.2<x<0.5. Here, the system is metallic and paramagnetic, but close to magnetic order, and a competition of a ferromagnetic and incommensurate antiferromagnetic instability determines the magnetic behaviour. An applied magnetic field induces a drastic change; we have studied this metamagnetic transition by inelastic neutron scattering, thereby probing the dynamic magnetic correlations at different magnetic fields and temperatures. We find that the ground state without magnetic field is determined by a near nesting instability of the Fermi surface. A magnetic field higher than the metamagnetic critical field suppresses these features and induces strong paramagnon scattering, proving the existence of strong ferromagnetic correlations.