When metal organic frameworks turn into linear magnets.

P. Canepa, Y. J. Cabal, T. Thonhauser; Phys. Rev. B 87, 094407 (2013).

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 quasilinear 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 one-dimensional (1D) magnets at low temperature. The interchain coupling is found to be antiferromagnetic, in agreement with experiments. While some quasi-1D materials exist that exhibit linear magnetism, mostly complex oxides, polymers, and a few other rare materials, 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.