title: Observation of hysteretic magnetic phase transitions coupled with orientation motion of ions and dielectric relaxation in a one-dimensional nickel-bis-dithiolene molecule solid.
abstract: The second polymorph, the β-crystal, of the nickel-bis-dithiolene compound [4'-CF3bzPy][Ni(mnt)2], where 4'-CF3bzPy = 1-(4'-trifluoromethylbenzyl)pyridinium and mnt(2-) = maleonitriledithiolate, was obtained. The variable-temperature single crystal structures, magnetic behavior in 1.8-300 K and dielectric nature in 123-373 K have been investigated for the β-crystal. This polymorph experiences two hysteretic magnetic phase transitions in a narrow temperature region (190-217 K) with the thermal hysteresis loops ca. 6 K and ca. 11 K. The two hysteretic magnetic phase transitions are coupled with two isostructural phase transitions (IPTs), respectively, which are driven by the novel step-wise dynamic orientation motion of the anion and cation in the β-crystal. There is an absence of a dielectric anomaly in the structural transformation temperature interval. However, a dielectric relaxation, related to the dipole motion of polar CF3 groups in the cations under an ac electrical field, emerges in the high-temperature phase.
authors.affiliation: State Key Laboratory of Materials-Oriented Chemical Engineering and College of Science, Nanjing University of Technology, Nanjing 210009, P. R. China.
authors.forename: Xuan-Rong
authors.initials: XR
authors.lastname: Chen
authors.forename: Wei-Hua
authors.initials: WH
authors.lastname: Ning
authors.forename: Hao
authors.initials: H
authors.lastname: Yang
authors.forename: Jian-Lan
authors.initials: JL
authors.lastname: Liu
authors.forename: Fang
authors.initials: F
authors.lastname: Xuan
authors.forename: Xiao-Ming
authors.initials: XM
authors.lastname: Ren