Structural Phase Transition in Two-Dimensional kagome Antiferromagnet m-N-Methylpyridinium α-nitronyl nitroxide・BF_4・1/3 (Acetone) (Condensed Matter : Structure, Mechanical and Thermal Properties)

概要

論文の詳細を見る
We found for the first time a structural phase transition in two-dimensional kagome antiferromagnet m-N-methylpyridinium α-nitronyl nitroxide (m-MPYNN)・BF_4・1/3 (acetone). As, below T_s = 128.7K, the intense satellite reflections are clearly observed at the modulation wave vector of q_s = (1/3, 1/3, 0), the unit cell of the low-temperature phase is enlarged to √<3a> × √<3a> × c. In the low-temperature phase, the space group is determined to be P3lc. The orientation of acetone molecules orders below T_s, leading to the lack of the three-fold axis. To confirm whether the low-temperature phase maintains a kagome-like network structure or not, we estimate the overlap integrals between the singly occupied molecular orbital wave functions of the MPYNN molecules by the extended Huckel method. The result is that all the overlap integrals are modified below T_s, suggesting that the system below T_s cannot be regarded as the uniform S = 1 kagome antiferromagnet.
社団法人日本物理学会の論文
2004-04-15