Pressure Effects on Emim[FeCl4], a Magnetic Ionic Liquid with Three-Dimensional Magnetic Ordering

• Published in: The journal of physical chemistry. B 2013-03, Vol.117 (11), p.3198-3206
• Main Authors: García-Saiz, Abel, de Pedro, Imanol, Blanco, Jesús A, González, Jesús, Fernández, Jesús Rodríguez
• Format: Article
• Language: English
• Subjects: Antiferromagnetism; Condensed matter: electronic structure, electrical, magnetic, and optical properties; Exact sciences and technology; Hydrostatic pressure; Ionic liquids; Magnetic liquids; Magnetic properties and materials; Magnetization; Neel temperature; Order disorder; Physics; Raman spectroscopy; Studies of specific magnetic materials; Three dimensional
• ISSN: 1520-6106; 1520-5207
• DOI: 10.1021/jp3114623

We report a combined study using magnetization and Raman spectroscopy on the magnetic ionic liquid 1-ethyl-3-methyl­imidazolium tetrachloro­ferrate, Emim­[FeCl4]. This material shows a long-range antiferromagnetic ordering below the Néel temperature T N ≈ 3.8 K. The effects of pressure on the magnetic properties have been studied using a miniature piston–cylinder CuBe pressure cell. This three-dimensional ordering is strongly influenced when hydrostatic pressure is applied. It is observed that low applied pressure is enough to modify the magnetic interactions, inducing a transition from antiferromagnetic to ferrimagnetic ordering. Raman spectroscopy measurements reveal important information about the existence of isolated [FeCl4]− anions and the absence of dimeric [Fe2Cl7]− units in the liquid and solid states. These features seem to suggest that the superexchange pathways responsible for the appearance of magnetic ordering are mediated through Fe-Cl–Cl-Fe. Furthermore, the liquid–solid phase transition exhibits a magnetic hysteresis near room temperature, which can be tuned by weak pressures.