Dresden 2006 – wissenschaftliches Programm

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TT: Tiefe Temperaturen

TT 25: Correlated Electrons - Poster Session

TT 25.94: Poster

Mittwoch, 29. März 2006, 14:30–18:30, P1

Metamagnetism of (Ca,Sr)₂RuO₄ studied by thermal expansion and magnetostriction — •J. Baier¹, M. Kriener¹, S. Stark¹, O. Heyer¹, T. Zabel¹, P. Steffens¹, O. Schumann¹, O. Friedt¹, A. Revcolevschi², S. Nakatsuji³, Y. Maeno³, T. Lorenz¹, M. Braden¹, and J. Mydosh¹ — ¹II. Phys. Institut, University of Cologne,Germany — ²Lab. de Physico-Chimie de lÉtat Solide,Université Paris-Sud, France — ³Dep. of Physics, KyotoUniversity, Japan

We present a study of the thermal expansion α(T,H) and the specific heat c_P(T,H) down to 300 mK near the metamagnetic transition in Ca_2−xSr_xRuO₄ with 0.2≤ x ≤ 0.5. Isovalent substitution of Sr by the smaller Ca drives the spin-triplet superconductor Sr₂RuO₄ to the antiferromagnetic Mott-insulator Ca₂RuO₄. At 0.2≤ x ≤ 0.5 the compounds are still metallic but close to localization. We find strong and anisotropic anomalies in α(T) which change sign in sufficiently high magnetic fields [1]. Striking similarities with the metamagnets Sr₃Ru₂O₇ and CeRu₂Si₂ are noticed. At x=0.2, the sign change of the thermal expansion anomaly coincides with the metamagnetic transition (MMT). This MMT is accompanied by a large anisotropic magnetostriction. Furthermore, c_P/T is unusually large and shows a non-monotonic field dependence with a maximum at the MMT which turns into a minimum above 2 K. In contrast, for x=0.5 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] Kriener et al., cond-mat 0408015, accepted for publication in PRL

Supported by the DFG through SFB 608