Strong Magnetocrystalline Anisotropy Arising from Metal–Ligand Covalency in a Metal–Organic Candidate for 2D Magnetic Order

Abstract

Layered metal–organic frameworks are promising candidates for new two-dimensional (2D) magnets, as the synthetic programmability of these materials can provide a route to diverse structural and electronic properties. However, such framework materials typically lack the heavy elements that engender magnetocrystalline anisotropy in the monolayer ferromagnets reported to date. Alternative sources of magnetic anisotropy are therefore needed in these materials. Here, we report the synthesis of single crystals of the framework material (NMe4)2[Fe2L3] (H2L = 3,6-dichloro-2,5-dihydroxybenzoquinone) and evaluate the angular dependence of its magnetic properties. Oriented-crystal magnetization measurements reveal strong uniaxial anisotropy, where the easy axis is aligned with the crystallographic c axis. While the spin carriers of this structure are isotropic S = 5/2 FeIII metal centers and S = 1/2 organic linkers, the anisotropy energy of the framework material is comparable to that of reported 2D ferromagnets. Density functional theory calculations indicate that the observed magnetocrystalline anisotropy arises from ligand-to-metal charge transfer that enhances the magnetic anisotropy of the otherwise-isotropic Fe centers, suggesting that metal–ligand covalency can be utilized as a general additive for the development of 2D magnets. These results show the possibility for (NMe4)2[Fe2L3] to retain magnetic order down to the 2D monolayer limit. In addition, the combination of large magnetic anisotropy and semiconducting character in (NMe4)2[Fe2L3] highlights its potential as a new 2D magnetic semiconductor.

van der Waals Heterostructures Based on Nanolayered Paramagnetic Tm(II) Compounds and Boron Nitride for Investigating Spin Frustration

“…Thin films have garnered significant interest recently, as they have been shown to exhibit unusual emergent properties. − The range of synthetic methods used to generate these materials includes chemical vapor deposition (CVD), liquid exfoliation, , chemical growth, spin-coating techniques (SCT), layer-by-layer (LbL) assembly deposition, and mechanical exfoliation of available layered solid-state materials. , Exfoliation is advantageous in that the bulk properties of a material can be elucidated prior to the generation of thin films.…”

Development of a magnetic hybrid material capable of photoinduced phase separation of iron chloride by shape memory and photolithography

“…Several mechanisms have been proposed to improve the magnetic susceptibility of Fe complexes by structural control, including reduction of the Fe( iii )–Fe( iii ) distance. 55–57 The range of Fe( iii )–Fe( iii ) distances that affect magnetic susceptibility are estimated to be in Å units. Here, structures created were in the μm scale, and the coupling effect of Fe( iii )–Fe( iii ) was not caused by structure, but by proximity of FeCl 3 , compressed in single units of microstructure.…”

Series of Benzoquinone-Bridged Dicobalt(II) Single-Molecule Magnets

“…Benzoquinones have been widely used in coordination and material chemistry as organic linkers that bind a variety of 3d or 4f metal ions into intriguing structural topologies with various physical properties. − Especially, benzoquinones are redox active and can be reversibly reduced to semiquinones via a one-electron process (even hydroquinones when accepting two electrons) when they coordinate to metal ions since their orbital energies were found close with those of the antibonding orbitals for the metal ions. Either substituting the 3,6-positioned H atoms by t Bu, NO 2 , CN, or halogens or replacing the O atoms with N or S ones may readily modify both the steric hindrances and the electronic potentials of such ligands. − As such, a large family of discrete molecules and extended frameworks with rich physicochemical properties were prepared.…”