Competition between helimagnetism and commensurate quantum spin correlations in LiCu2O2 |
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Authors: | Masuda T Zheludev A Bush A Markina M Vasiliev A |
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Affiliation: | Condensed Matter Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831-6393, USA. |
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Abstract: | Neutron diffraction and bulk measurements are used to determine the nature of the low-temperature ordered state in LiCu2O2, a S=1/2 spin-chain compound with competing interactions. The spin structure is found to be helimagnetic, with a propagation vector (0.5,zeta,0), zeta=0.174. The nearest-neighbor exchange constant and frustration ratio are estimated to be J(1)=5.8 meV and J(2)/J(1)=0.29, respectively. For idealized quantum spin chains, these parameter values would signify a gapped spin-liquid ground state with commensurate spin correlations. The observed temperature dependence of the magnetic propagation vector in LiCu2O2 is attributed to a competition between incommensurate helimagnetism in the classical spin model and commensurability in the quantum case. It is also proposed that long-range ordering in LiCu2O2 is facilitated by intrinsic nonstoichiometry. |
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