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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. Mydosh11II. 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 cP(T,H) down to 300 mK near the metamagnetic transition in Ca2−xSrxRuO4 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, cP/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 cp/T in a magnetic field similar to the behavior of cp/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

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