When metal organic frameworks turn into linear magnets

TL;DR

This paper demonstrates that MOF-74 materials exhibit strong ferromagnetic chains with weak anti-ferromagnetic inter-chain coupling, making them nearly perfect 1D magnets, which are easy to synthesize and useful for studying low-temperature 1D magnetism.

Contribution

It reveals that MOF-74 compounds are natural realizations of 1D Ising magnets with significant ferromagnetic chain coupling and minimal inter-chain interactions, a novel finding in MOF research.

Findings

MOF-74 exhibits ferromagnetic chains with strong coupling.

Inter-chain coupling is an order of magnitude weaker and anti-ferromagnetic.

MOF-74 is a simple, easily synthesized 1D magnetic material.

Abstract

We investigate the existence of linear magnetism in the metal organic framework materials MOF-74-Fe, MOF-74-Co, and MOF-74-Ni, using first-principles density functional theory. MOF-74 displays regular quasi-linear chains of open-shell transition metal atoms, which are well separated. Our results show that within these chains-for all three materials-ferromagnetic coupling of significant strength occurs. In addition, the coupling in-between chains is at least one order of magnitude smaller, making these materials almost perfect 1D magnets at low temperature. The inter-chain coupling is found to be anti-ferromagnetic, in agreement with experiments. While some quasi-1D materials exist that exhibit linear magnetism-mostly complex oxides, polymers, and a few other rare material-they are typically very difficult to synthesize. The significance of our finding is that MOF-74 is very easy to synthesize and it is likely the simplest realization of the 1D Ising model in nature. MOF-74 could thus be used in future experiments to study 1D magnetism at low temperature.