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TT: Tiefe Temperaturen

TT 30: Postersitzung IV: Kritische Ph
änomene, Quantenstörstellen, niederdimensionale Systeme

TT 30.43: Poster

Thursday, March 11, 2004, 14:30–19:00, Poster A

Thermodynamic Properties of Layered Ruthenates — •J. Baier¹, T. Zabel¹, M. Kriener¹, M. Reuther¹, T. Lorenz¹, A. Freimuth¹, P. Steffens¹, O. Friedt¹, M. Braden¹, A. Revcolevschi², S. Nakatsuji³, and Y. Maeno³ — ¹II. Physikalisches Institut, Universität zu Köln, Germany — ²Laboratoire de Physico-Chimie de lEtat Solide, Universite Paris-Sud, Orsay, France — ³Department of Physics, Kyoto University, Japan

The phase diagram of Ca_2−xSr_xRuO₄ presents a rich spectrum of distinct structural distortions, which are accompanied by drastic changes of the magnetic and electronic properties [1]. Ca-Doping drives the system from the spin-triplet superconductor Sr₂RuO₄ to the antiferromagnetic Mott-insulator Ca₂RuO₄. At x=0.5, the low-temperature magnetic susceptibility is considerably increased and an unusually large C_p/T-value due to the evolution of a nearly ferromagnetic heavy-mass Fermi liquid is observed [2]. We find an anomalous, anisotropic thermal expansion for this compound. In a magnetic field, the anomalous thermal expansion and the large C_p/T-value are suppressed with an anisotropic field dependence. For lower x, an additional tilting of the RuO₆ octahedra sets in and at x=0.2 the susceptibility is again strongly reduced [2]. In high magnetic fields this compound is driven through a metamagnetic transition and the large susceptibility recovers. We observe a large magnetostriction during this metamagnetic transition.

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

[2] S. Nakatsuji et al., Phys. Rev. Lett. 90 (2003)

Supported by the DFG through SFB 608