Comment on 'Competition between Helimagnetism and Commensurate Quantum Spin Correlations in LiCu_2O_2'

摘要

In a neutron scattering investigation of LiCu_2O_2 Masuda et al. reported the direct observation of an incommensurate (IC) magnetic structure below 22 K. Though this study confirms similar indirect IC observations pointing to the presence of frustrated magnetic interactions, they deserve now more detailed work to elucidate the microscopic origin of that frustration. We will show that the adopted antiferromagnetic (AFM) double-chain (DC) Heisenberg model [Fig. 1(a)] suggests an unrealistic frustration scenario for LiCu_2O_2. It should be replaced by a ferromagnetic-(FM)-AFM frustrated single-chain model [Fig. 1(b)]. Based on electronic structure (LDA) and cluster calculations as well as a phenomenol-gical analysis of the magnetic susceptibility χ(T), we arrive at opposite estimates compared with Ref. with respect to the magnitude or sign of the main couplings.