One-dimensional magnetic order in the metal-organic framework Tb(HCOO)3

TL;DR

This study investigates the emergence of one-dimensional magnetic order in the MOF Tb(HCOO)3 using neutron scattering, simulations, and analysis, revealing partial ferromagnetic ordering and frustration effects at low temperatures.

Contribution

It demonstrates the presence of low-dimensional magnetic order in a MOF, highlighting the role of architecture in stabilizing such states and exploring their physical properties.

Findings

Magnetic transition involves one-dimensional ferromagnetic ordering.

Partial order with frustrated antiferromagnetic alignment between chains.

Neutron scattering peaks indicate low-dimensional magnetic correlations.

Abstract

A combination of variable-temperature neutron scattering, reverse Monte Carlo analysis and direct Monte Carlo simulation is used to characterise the emergence of magnetic order in the metal--organic framework (MOF) Tb(HCOO)$_3$ over the temperature range 100 K to 1.6 K $=T_{\rm N}$. We show that the magnetic transition at $T_{\rm N}$ involves one-dimensional ferromagnetic ordering to a partially-ordered state related to the triangular Ising antiferromagnet. In this phase, the direction of magnetisation of ferromagnetic chains tends to alternate between neighbouring chains but this alternation is frustrated and is not itself ordered. In neutron scattering measurements this partial order gives rise to Bragg-like peaks, which cannot be interpreted using conventional magnetic crystallography without resort to unphysical spin models. The existence of low-dimensional magnetic order in Tb(HCOO)$_3$ is stabilised by the contrasting strength of inter- and intra-chain magnetic coupling, itself a consequence of the underlying MOF architecture. Our results demonstrate how MOFs may provide an attractive if as yet under-explored platform for the realisation and investigation of low-dimensional physics.