Shin-ichiro Tani, Hiroaki Inoue, Takao Suzuki, Shigeharu Hosoya, Kaori Inokuchi, Takao Fujiwara, Takayuki Goto, Hidekazu Tanaka, Takahiko Sasaki, Satoshi Awaji, Kazuo Watanabe, Norio Kobayashi
Progress of theoretical physics. Supplement. 159(159) 235-240 2005年
Cu-NMR study under high-field up to 17T has been performed on the three-dimensional spin dimer system NH_4CuCl_3, which shows the two-stepped magnetization plateaus. The local magnetization of Cu-site measured by NMR showed a significant deviation from the macroscopic magnetization at low temperatures, suggesting the localization of the field-induced triplons. In the high field region around 16 T, two inequivalent Cu sites are observed. Only one of the two sites shows a split in the resonance line below T_N≃3.2K, indicating the existence of the field-induced magnetic order, to which a part of spins in the system participate.