Zaharko, O.Ronnow, H.Mesot, J.Crowe, S. J.Paul, D. M.Brown, P. J.Daoud-Aladine, A.Meents, A.Wagner, A.Prester, M.Berger, H.2007-01-242007-01-242007-01-24200610.1103/PhysRevB.73.064422https://infoscience.epfl.ch/handle/20.500.14299/239956WOS:0002356686000658183Polarized and unpolarized neutron-diffraction studies have been carried out on single crystals of the coupled spin tetrahedra systems Cu2Te2O5X2 (X=Cl, Br). A model of the magnetic structure associated with the propagation vectors k(') (Cl) approximate to (-0.150,0.422, (1)/(2)) and k'(Br) approximate to (-0.172,0.356, (1)/(2)) and stable below T-N = 18 K for X= Cl and T-N = 11 K for X = Br is proposed. A feature of the model, common to both the bromide and chloride, is a canted coplanar motif for the four Cu2+ spins on each tetrahedron which rotates on a helix from cell to cell following the propagation vector. The Cu2+ magnetic moment determined for X = Br, 0.395(5)mu(B), is significantly less than for X= Cl, 0.88 (1)mu(B) at 2 K. The magnetic structure of the chloride associated with the wave vector k' differs ;from that determined previously for the wave vector k approximate to (0.150,0.422, (1)/(2))SLOW-NEUTRONSSCATTERINGCLUSTERSCLBRtext::journal::journal article::research article