Hamburg 2001 – scientific programme
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TT: Tiefe Temperaturen
TT 6: Postersitzung I: Josephsonkontakte und SQUIDs, Supraleitung: Theorie, Korrelierte Elektronen, Niederdimensionale Systeme, Magnetotransport, Quantenhalleffekt, Kohlenstoff-Nanoröhrchen, Quantenflüssigkeiten
TT 6.65: Poster
Monday, March 26, 2001, 14:30–17:00, Rang S\ 3
Magnetic properties of the spin-tetrahedra systems Cu2Te2O5X2 (X=Cl, Br) — •P. Lemmems1, K.Y. Choi1, G. Güntherodt1, E. Kaul2, Ch. Geibel2, K. Becker3, W. Brenig4, C. Gros5, R. Valenti5, M. Johnsson6, F. Mila7, and P. Millet8 — 12. Phys. Inst., RWTH Aachen — 2MPI-CPfS, Dresden — 3Inst. f. Theor. Physik, TU-Dresden — 4Inst. f. Theor. Physik, TU-Braunschweig — 5Inst. f. Theor. Physik, Univ. Saarbrücken — 6Dept. of Inorg. Chem., Stockholm Univ., Stockholm, Sweden — 7Inst. de Phys. Theor., Univ. Lausanne, Switzerland — 8CEMES/CNRS, Toulouse, France
We have studied the magnetic properties of the
spin-tetrahedra systems Cu2Te2O5X2(X=Cl, Br) by means of
magnetic susceptibility, specific heat and Raman scattering. An analysis
of the magnetic susceptibility χ(T) shows a large singlet-triplet
spin gap Δ≈40 K. Furthermore, evidence for a magnetic
instability exists for T≈10 K in χ(T) and in the specific
heat. The magnetic excitation spectrum investigated by light scattering
experiments shows a broad continuum at 2Δ and a soft mode at
smaller energies. Theoretical studies reveal the significance of the
dimensionality and the inter-tetrahedra coupling for the ground state and
the excitation spectrum of this peculiar spin topology.
Work
supported by DFG.