Evidence for an unconventional magnetic instability in the spin-tetrahedra system Cu(2)Te(2)O(5)Br(2).
- Lemmens, P.
- Choi, K.Y.
- Kaul, E.E.
- Geibel, C.
- Becker, K.
- Brenig, W.
- Valenti, R.
- Gros, C.
- Johnsson, M.
- Millet, P.
- Mila, F.
Publication date
January 2001
DOI Publisher
American Physical Society (APS)Abstract
Thermodynamic experiments as well as Raman scattering have been used to study the magnetic instabilities in the spin-tetrahedra systems Cu(2)Te(2)O(5)X(2), X = Cl and Br. While the phase transition observed in the Cl system at T(N) = 18.2 K is consistent with 3D antiferromagnetic ordering, the phase transition at T(o) = 11.4 K in the Br system has several unusual features. We propose an explanation in terms of weakly coupled tetrahedra with a singlet-triplet gap and low-lying singlets
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