[Cs₆Cl][Fe₂₄Se₂₆]: A Host–Guest Compound with Unique Fe–Se Topology

Abstract

The novel host-guest compound [Cs6Cl][Fe24Se26] (I4/mmm; a=11.0991(9), c=22.143(2) Å) was obtained by reacting Cs2Se,CsCl, Fe, and Se in closed ampoules. This is the first member of a family of compounds with unique Fe-Se topology, which consists of edge-sharing, extended fused cubane [Fe8Se6Se8/3] blocks that host a guest complex ion, [Cs6Cl](5+). Thus Fe is tetrahedrally coordinated and divalent with strong exchange couplings, which results in an ordered antiferromagnetic state below TN =221 K. At low temperatures, a distribution of hyperfine fields in the Mössbauer spectra suggests a structural distortion or a complex spin structure. With its strong Fe-Se covalency, the compound is close to electronic itinerancy and is, therefore, prone to exhibit tunable properties.

Metal Vacancy Ordering in an Antiperovskite Resulting in Two Modifications of Fe2SeO

“…The other phase, consisting of square prisms, was dominating in the solidified salt melt (β in Figure ). Single crystals of a third compound, [Cs 6 Cl][Fe 24 Se 26 ], were also found in the sample, but this is discussed elsewhere . Extensive optimization of the solid‐state reaction afforded samples where different modifications dominated (see the Supporting Information, Section S1), but high purities were not achieved.…”

Pressure-induced collapse of large-moment magnetic order and localized-to-itinerant electronic transition in the host-guest compound [Cs6Cl][FAdler1, Medvedev2, Valldor3 et al. 2020Phys. Rev. BSelf Cite2010View full textAdd to dashboardCite

“…% pure, having 1% CsCl, 2% Fe 3 Se 4 [25], and 1-2% of an unknown secondary phase. The main compound is the title compound, as diffraction intensities match very well with expectations and the refined unit cell parameters (a = 11.074(3) and c = 22.10(1) Å only deviate less than ∼0.2% as compared to the previously re- [22], the spectrum at 230 K can be described by a single quadrupole doublet, which arises from the two crystallographically distinct sites that are, however, similar in their local coordination environment and thus not resolved in the spectrum. The spectrum confirms that the material is magnetically disordered at 230 K. In contrast to the earlier sample, a weak additional hyperfine pattern is discernible, which is assigned to an impurity.…”

“…The pressure was determined by the ruby luminescence method. The resistivity results shown in this work were obtained on a sample of [Cs 6 Cl][Fe 24 Se 26 ] without 57 Fe enrichment from our previous study [22] due to the higher sample purity. However, for checking the reproducibility, high-pressure resistivity measurements on the 57 Fe enriched sample were also performed.…”

Metal Vacancy Ordering in an Antiperovskite Resulting in Two Modifications of Fe2SeO

“…Single crystals of a third compound, [Cs 6 Cl][Fe 24 Se 26 ], were also found in the sample, but this is discussed elsewhere. [6] Extensive optimization of the solid-state reaction afforded samples where different modifications dominated (see the Supporting Information, Section S1), but high purities were not achieved. By investigating samples that were quenched at different reaction temperatures, the a-phase proved to be metastable whereas the b-phase is stable within a narrow temperature range (Section S2).…”

“…Each Fe/O lattice can also be described in terms of vertex-sharing OFe 4 tetrahedra, with a crystal structure similar to that of an antisilicate. Iron is divalent and has a high-spin d 6 (S = 2) configuration. The b-phase exhibits magnetoelectric coupling.…”