Dresden 2003 – wissenschaftliches Programm
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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. Löhneysen1,2, 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 2F5/2 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).