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TT: Tiefe Temperaturen

TT 14: Postersitzung III (Neue u. unkonventionelle Supraleiter, Anwendungen der Supraleitung, Dünne Schichten, JJs und SQUIDs, Schwere Fermionen, Kondo-Systeme)

TT 14.48: Poster

Mittwoch, 26. März 2003, 14:30–19:00, P2c

Low-temperature thermal expansion of CeBiPt — •R. Lortz¹, G. Goll², K. Grube¹, C. Meingast¹, H. v. Löhneysen^1,2, and T. Takabatake³ — ¹Forschungszentrum Karlsruhe, Institut für Festkörperphysik, 76021 Karlsruhe — ²Physikalisches Institut, Universität Karlsruhe, 76128 Karlsruhe — ³Department of Quantum Matter, ADSM, Hiroshima University Higashi-Hiroshima 739-8526, Japan

CeBiPt is a low-carrier-density semimetal (n=7.7· 10¹⁷ cm⁻³). Shubnikov-de Haas (SdH) experiments [1] suggest an unusual temperature dependence of the Fermi surface cross section parallel to [100]. The 4f¹ electron configuration of the Ce³⁺ ion forms a ²F_5/2 groundstate with J = 5/2 according to Hund’s rules. The sixfold level degeneracy is lifted by the cubic crystal symmetry into a doublet and a quadruplet state. We measured the thermal expansivity α down to 2 K in zero and applied magnetic field B. In B > 0 the fourfold degeneracy of the Γ₈ groundstate is lifted by the Zeeman splitting. The low-energy thermal exitations are seen as a minimum in the temperature dependence of the longitudinal thermal expansivity. The minimum in α(T) is shifted to higher T as B is increased. The magnetostriction, i. e. the relative length change Δ L(B)/L(0) as a function of B, was determined as well. Although a relative large length change was measured for both directions Δ L ∥ [100] and Δ L ∥ [110], no significant anisotropy was found which could account for the anisotropic behavior of the Fermi surface seen in the SdH experiments [1].
[1] G. Goll et al., Europhys. Lett. 57, 233 (2002).