Dresden 2003 – scientific programme
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TT: Tiefe Temperaturen
TT 6: Postersitzung I (Amorphe- u. Tunnelsysteme, Niedrigdimensionale Systeme, Supraleitung: Elektronenstruktur, Phononen, Tunneln, Ordnungsparameter)
TT 6.26: Poster
Monday, March 24, 2003, 14:30–19:00, P2c, P2d
Magnetic order in the tetrahedral quantum spin system Cu2Te2O5(Br1−xClx)2 — •H.-H. Klauss1, P. Lemmens1, A. Bosse1, D. Baabe1, D. Mienert1, H. Luetkens1, F.J. Litterst1, K.-Y. Choi2, R. Scheuermann3, and M. Johnsson4 — 1Institut für Metallphysik und Nukleare Festkörperphysik, TU Braunschweig — 2II. Physikalisches Institut, RWTH Aaachen — 3Paul Scherrer Institut, Villigen, Switzerland — 4Department of Inorganic Chemistry, Stockholm University, Sweden
We present studies of the magnetic correlations in the weakly coupled spin tetrahedra system Cu2Te2O5(Br1−xClx)2. Due to quantum fluctuations these systems show strongly reduced magnetic transition temperatures TNCl = 18.2 K and TNBr = 11.4 K in comparison with a magnetic exchange of J ≈ 40 K. Susceptibility, specific heat and magnetic raman scattering experiments reveal that the Bromide system (x = 0) is close to a quantum phase transition (P. Lemmens et al. PRL 87 227201 (2001)). We performed muon spin relaxation (µSR) experiments on six samples with 0 ≤ x ≤ 1. All samples show two spontaneous muon spin precession frequencies below their respective ordering temperatures which decrease monotonously with decreasing x. An enhanced longitudinal spin relaxation is attributed to the dominantly low dimensional character of the system.