Abstract
We report on the nature of the low temperature magnetic ordering of a magnetic ionic plastic crystal, Choline[FeCl4]. This investigation was carried out using heat capacity measurements, neutron diffraction experiments and muon spin relaxation (μSR) spectroscopy. The calorimetric measurements show the onset of an unusual magnetic ordering below 4 K with a possible second magnetic phase transition below 2 K. Low temperature neutron diffraction data reveal a three dimensional antiferromagnetic ordering at 2 K compatible with the previous magnetometry results. The analysis of μSR spectra indicates a magnetic phase transition below 2.2 K. At 1.6 K, the analysis of the shape of the μSR spectra suggests the existence of an additional magnetic phase with features of a possible incommensurate magnetic structure.
Highlights
Plastic crystal materials were described by Timmermans in the 1960s
The most striking features are an enhancement of the rotational motion of [Choline]+ and [FeCl4]- anions with increasing temperature up to the melting point, 490 K, and the presence of a three-dimensional magnetic ordering below 4 K [5]. In this contribution we focus on the nature of the low temperature magnetic ordering of this compound combining heat capacity measurements, neutron diffraction data and muon spin relaxation spectroscopy
The μSR experiments were performed in zero applied field at the Laboratory for Muon Spin Spectroscopy of the Paul Scherrer Institute, Switzerland using the GPS spectrometer in the temperature range 2–200 K
Summary
Plastic crystal materials were described by Timmermans in the 1960s. These compounds, composed entirely of ions, display an intermediate phase between the solid and the liquid state called plastic phase. The most striking features are an enhancement of the rotational motion of [Choline]+ and [FeCl4]- anions with increasing temperature up to the melting point, 490 K, and the presence of a three-dimensional magnetic ordering below 4 K [5].
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