Incommensurate magnetism in the coupled spin tetrahedra system Cu₂Te₂O₅Cl₂

• Datum: 2005
• Hauptverfasser: Zaharko, O., Ronnow, H.M., Daoud-Aladine, A., Streule, S., Juranyi, F., Mesot, J., Berger, H., Brown, P.J.
• Format: Artikel
• Sprache: English
• Veröffentlicht: Фізико-технічний інститут низьких температур ім. Б.І. Вєркіна НАН України 2005
• Schriftenreihe: Физика низких температур
• Schlagworte: К семидесятилетию антиферромагнетизма
• Online Zugang: https://nasplib.isofts.kiev.ua/handle/123456789/121701
• Назва журналу: Digital Library of Periodicals of National Academy of Sciences of Ukraine
• Zitieren: Incommensurate magnetism in the coupled spin tetrahedra system Cu₂Te₂O₅Cl₂ / O. Zaharko, H.M. Ronnow, A. Daoud-Aladine, S. Streule, F. Juranyi, J. Mesot, H. Berger, P.J. Brown // Физика низких температур. — 2005. — Т. 31, № 8-9. — С. 1068-1072. — Бібліогр.: 17 назв. — англ.

Neutron scattering studies on powder and single crystals have provided new evidences for unconventional magnetism in Cu₂Te₂O₅Cl₂. The compound is built from tetrahedral clusters of S = 1/2 Cu²⁺ spins located on a tetragonal lattice. Magnetic ordering, emerging at TN = 18.2 K, leads to a very complex multi-domain, most likely degenerate, ground state, which is characterized by an incommensurate (ICM) wave vector k ~ [0.15, 0.42, 1/2]. The Cu²⁺ ions carry a magnetic moment of 0.67(1) μB/Cu²⁺ at 1.5 K and form a four helices spin arrangement with two canted pairs within the tetrahedra. A domain redistribution is observed when a magnetic field is applied in the tetragonal plane (Hc ≈ 0.5 T), but not for H||c up to 4 T. The excitation spectrum is characterized by two well-defined modes, one completely dispersionless at 6 meV, the other strongly dispersing to a gap of 2 meV. The reason for such complex ground state and spin excitations may be geometrical frustration of the Cu²⁺ spins within the tetrahedra, intra- and inter-tetrahedral couplings having similar strengths and strong Dzyaloshinski–Moriya anisotropy. Candidates for the dominant intra- and inter-tetrahedral interactions are proposed.