Cl-NMR study on field-induced magnetic order in quasi-one-dimensional antiferromagnet (CH3)2CHNH3CuCl3

(CH3)2CHNH3CuCl3 is described as the spin ladder system, which is composed of a strong ferromagnetic rung and a weak antiferromagnetic leg. Since the ferromagnetic dimer behaves like S = 1 spin, this system can be treated as the S = 1 quasi-one-dimensional antiferromagnet spin chain (so-called Haldane chain). Cl-NMR study under high-field up to 17.5T has been carried out in order to investigate the field-induced magnetic order in this system. In the lower field region below 10T, the signals from Cl-sites were observed as sharp NMR lines. These paramagnetic lines showed the split above HredN 12T (T = 1.85K), demonstrating the existence of the staggered field due to the field-induced magnetic order. Around HN, the resonance lines disappeared due to the critical slowing down when the applied magnetic field was perpendicular to the ladder, whereas they did not when the field was nearly parallel to the ladder. These results indicate that the spin dynamics around the field-induced magnetic order is anisotropic in this system.