Magnetic properties of a S = 1/2 zigzag spin chain compound (N₂H₅)CuCl₃

Large-scale Computational Science Division, Cybermedia Centre, Osaka University 1-32 Machikaneyamacho, Toyonaka, Osaka 560-0043, JapanWe present a theoretical and experimental study of a quasi-one-dimensional zigzag antiferromagnet (N₂H₅)CuCl₃, which can be viewed as weakly coupled Heisenberg chains with a frustrated interaction. We first discuss generic features of the magnetic properties of the zigzag spin chain between the nearly single chain case and the nearly double chain case, on the basis of the finite temperature density-matrix renormalization group (DMRG) calculations. We next show the experimental results for the magnetic susceptibility and the high-field magnetization of a single crystal of (N₂H₅)CuCl₃ above the Néel temperature T_N = 1.55 K. By comparing the experimental data with the DMRG results carefully, we finally obtain the ratio of the nearest and next-nearest exchange couplings as J₁/₂ = 0.25 with J₂/k_B = 16.3K. We also investigate the three-dimensional (3D) coupling J′ effect by using mean-field theory combined with the DMRG calculations. The estimated value J′ ∼ 0.04 J₂ supports the one-dimensionality of (N₂H₅)CuCl₃ above T_N.