Inelastic neutron scattering study on magnetic excitation of '-(BEDT-TTF)ICl

中性子非弾性散乱による'-(BEDT-TTF)IClの磁気励起の研究

河村 聖子   ; 谷口 弘三*; 松浦 直人*; 古府 麻衣子*   ; 村井 直樹  ; 佐々木 孝彦*

Kawamura, Seiko; Taniguchi, Hiromi*; Matsuura, Masato*; Kofu, Maiko*; Murai, Naoki; Sasaki, Takahiko*

Charge-transfer complex '-(BEDT-TTF)ICl is a dimer-Mott insulator having a two-dimensional (2D) structure of the BEDT-TTF dimers and the ICl anion layers. The system exhibits a long-range antiferromagnetic order below ~K. It has also been reported that a new type of field-induced glassy ferroelectricity occurs in this system below ~K. We have tried to perform INS measurement on non-deuterated (h8) '-(BEDT-TTF)ICl to observe its magnetic excitation spectra reflecting the highly 2D magnetic correlation of the system. In the wave vector ()-energy () map, excitation signals at Q = (H 0.5 0) and its equivalent position (H -0.5 0) are observed. No dispersive excitation is observed along the a* axis, which corresponds to the layer stacking direction. The intra-layer excitation signal is observed up to ~45 K, indicating that the magnetic correlation within the layer survives up to temperature twice higher than . The present study shows the direct evidence of the strongly 2D magnetic interaction of '-(BEDT-TTF)ICl.