Low Temperature Magnetic Properties of a New Quasi-one-dimensional Organic Magnet α-2-Cl-4-F-V

We examine low-temperature magnetic properties of a new verdazyl radical crystal α-2-Cl-4-F- V. Molecular orbital calculations predict that this material is a spin-1/2 quasi-one-dimensional antiferromagnet; the exchange interaction is strongest in the chains along the b axis, whereas there are three interchain coupling parameters, the ratio of which are 0.06 ∼ 0.14 to the intrachain. The magnetization curve at 0.1 K shows gapless behavior like conventional one- dimensional quantum spin systems and saturates at about 5 T. A peak is observed in the temperature dependence of the heat capacity at 0 T, indicating that a three-dimensional ordering occurs at about 0.2 K. On the other hand, the temperature dependence of the magnetization at various magnetic fields shows an anomaly similar to that observed in many of gapped spin systems. This behavior is attributed to the highly frustrated nature of the interchain interactions.