Evidence for an unconventional magnetic instability in the spin-tetrahedra system Cu(2)Te(2)O(5)Br(2).
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.
Lemmens
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P
2. Physikalisches Institut, RWTH Aachen, D-56056 Aachen, Germany.
Choi
K Y
KY
Kaul
E E
EE
Geibel
C
C
Becker
K
K
Brenig
W
W
Valenti
R
R
Gros
C
C
Johnsson
M
M
Millet
P
P
Mila
F
F