Polar Ferromagnetic Metal by Intercalation of Metal–Amine Complexes

Abstract

The metal−amine complex Co(en) 3 , where en = ethylenediamine, intercalates between layers of cobalt sulfide (CoS) to form a polar, ferromagnetic metal. We solve the structure of the hybrid compound [Co(en) 3 ](CoS) 12 •en in the polar group Pca2 1 with lattice parameters a = 14.778(3) Å, b = 11.066(3) Å, and c = 20.095(5) Å using single-crystal X-ray diffraction. The [Co(en) 3 ] 2+ complexes order between CoS layers and break their inherent fourfold symmetry. Moreover, the chiral Co(en) 3 complexes hydrogen bond to the terminal sulfides of the layers and break inversion symmetry, thereby inducing a polar state. The shortest hydrogen bond of the amino group is H•••S = 2.41(1) Å. From 1.8 to 300 K, the title compound displays metallic electrical resistivity and an anomaly at 43 K. Through magnetization measurements, we find that Co(en) 3 exhibits spontaneous ferromagnetic order below 43 K. First-principles calculations reproduce the ferromagnetic structure and illustrate decoupling between the conducting electrons and the inversion-lifting distortion. Our work shows that hybrid materials created from intercalation chemistry of functional 2D hosts provides a pathway for uniting contraindicated properties.

Pseudo-Polymorphism in Layered FeS Intercalates: A Competition between Charged and Neutral Guest Species

“…The main difference between Co and Fe compounds is that the Co-S layer is fully occupied, and no Co vacancies are present, plus the ratio of intercalated en and tris-en complexes is 1:1 for the Co compound. 29 An expanded ab-plane could highlight vacancy ordering in the Fe-S layer or order within the intercalate or both, as observed in the crystal structure of compound 1. Ethylenediamine has a weak ligand field and [Fe(en) 3 ] 2+ complexes are expected to be high-spin.…”

“…Recently, a 4a×3b×c superstructure was reported for the intercalated CoS, [Co(en) 3 ](CoS) 12 •en, crystallizing in the polar Pca2 1 space group. 29 The structure was determined by means of single-crystal X-ray diffraction. Renormalizing the composition to 10 S atoms results in [Co 10 S 10 ][Co(en) 3 ] 0.83 • en 0.83 , which is close but not identical to composition proposed in current work for compound 2, [Fe 9.4(2) S 10 ][Fe(en) 3 ] 0.6(1) • en 0.9 (3) .…”

As–Se Pentagonal Linkers to Induce Chirality and Polarity in Mixed-Valent Fe–Se Tetrahedral Chains Resulting in Hidden Magnetic Ordering

“…Although the octahedral complexes such as tris-[Fe­(en) 3 ] 2+ are chiral, presence of both Δ- and Λ-isomers in solution makes most of the compounds crystallize in centrosymmetric space groups. An exception to this rule was recently reported for a Co–Se layered hybrid compound . In the current work, we hypothesize that chiral low-dimensional Fe–Se fragments can be stabilized using chiral inorganic covalent linkers, such as As–Se rings.…”

“…An exception to this rule was recently reported for a Co−Se layered hybrid compound. 20 In the current work, we hypothesize that chiral low-dimensional Fe−Se fragments can be stabilized using chiral inorganic covalent linkers, such as As−Se rings.…”

Formation of a Polar Structure in the Metallic Niobium Sulfide Nb4S3

“…Polar metals are an unusual class of material because, in general, metallic electrons act to screen electric fields within a material, thereby preventing long-range dipole–dipole interactions from stabilizing polar distortions. They have attracted significant research attention because of their connections to unconventional superconductivity and multiferroicity. , The origins of polarity in metals have been the subject of significant recent research interest because of the discovery of ferroelectric-like behavior in the polar metals LiOsO 3 (which undergoes a thermal polar–nonpolar phase transition) and WTe 2 (which can undergo ferroelectric switching) . Especially in the case of LiOsO 3 , the underlying cause of polarity in metals has been a matter of debate between size mismatch and imperfect electronic screening, with evidence for the latter having been found directly by the observation of relaxation dynamics …”