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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
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Abstract

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) mB/ 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 6.0 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.

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O. Zaharko, H. M. Ronnow, A. Daoud-Aladine, S. Streule, F. Juranyi, J. Mesot, H. Berger, P. J. Brown. 2005-02-07. Incommensurate magnetism in the coupled spin tetrahedra system Cu2Te2O5Cl2. https://doi.org/10.1063/1.2008143

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