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Berlin 2005 – scientific programme

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TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.74: Poster

Saturday, March 5, 2005, 11:00–16:30, Poster TU C

Structural properties of Ca2−xSrxRuO4 — •O. Schumann1, P. Steffens1, R. Müller1, G. Andre2, P.G. Radaelli3, P. Adelmann4, S. Nakatsuji5, Y. Maeno5, and M. Braden11II. Physikalisches Institut, Universität zu Köln — 2Laboratoire Léon Brillouin — 3ISIS Facility, Rutherford Appleton Laboratory — 4Forschungszentrum Karlsruhe, IFP — 5Department of Physics, Kyoto University

We present our x-ray- and neutron diffraction work on Ca2−xSrxRuO4 which shows an astonishing rich phase diagram, even though the substitution of Sr2+ by Ca2+ is an isovalent one [1]. Pure Sr2RuO4 (x=2) exhibits no structural distortions. Upon Ca-doping a rotation of the RuO6-octahedron sets in. This phase transition is strongly discontinuous, although a continuous one is allowed by symmetry. At rather higher Ca-content (x∼0.2) a metamagnetic transition is observed. The temperature and magnetic field dependence of small structural changes are an indication of an electron transfer between in- and out-of-plane t2g-orbitals. This transfer is driven by a van-Hove singularity in one of the concerned bands [2]. At even higher Ca-content the rotational distortion changes its stacking sequence. While for x>0.2 the octahedrons in neighboring layers rotate out of phase, for x<0.2 the rotation between neighboring layers is in-phase. This rather subtle change is in coincidence with a change of the ground state properties of the samples (metallic vs. af insulating).

[1] O.Friedt et al., Phys. Rev. B 63 174432 (2001)

[2] M.Kriener et al., condmat/0408015

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