Berlin 2005 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 16: Posters Correlated Electrons, Measuring Devices, Cryotechnique

TT 16.75: Poster

Samstag, 5. März 2005, 11:00–16:30, Poster TU C

Magnetic Field Dependence of Thermodynamic Properties of (Ca,Sr)₂RuO₄ — •J. Baier¹, T. Zabel¹, M. Kriener¹, P. Steffens¹, O. Schumann¹, O. Heyer¹, T. Lorenz¹, A. Freimuth¹, O. Friedt¹, M. Braden¹, A. Revcolevschi², S. Nakatsuji³, and Y. Maeno³ — ¹II.Physikalisches Institut, Universität zu Köln, Germany — ²Lab. de Physico-Chimie de lÉtat Solide, Université Paris-Sud, France — ³Dep. of Physics, Kyoto University, Japan

We present a study of thermal expansion α and specific heat c_P of Ca_2−xSr_xRuO₄ in magnetic fields. This series with the spin-triplet superconductor Sr₂RuO₄ and the antiferromagnetic Mott-insulator Ca₂RuO₄ as end members presents a rich spectrum of structural distortions accompanied by drastic changes of the magnetic and electronic properties [1]. We focus on 0.2≤ x ≤ 0.5 where the compound is still metallic but close to localization. We find an anisotropic anomalous thermal expansion. The anomaly is suppressed by a magnetic field [2]. Below T ≃ 20 K, α, c_P and the magnetization show an anisotropic field dependence. The x=0.2 sample shows a metamagnetic transition (MMT) accompanied by a large magnetostriction. Furthermore, c_P/T shows a non-monotonic field dependence with a maximum at the MMT. For x=0.5, c_p/T reaches an unusually large value in zero field and we observe a strong decrease of c_p/T in a magnetic field similar to the behavior of c_p/T at x=0.2 above the MMT.

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

[2] Kriener et al., cond-mat 0408015, submitted to Phys. Rev. Lett.

Supported by the DFG through SFB 608