Abstract
In the dense metal-organic framework Na[Mn(HCOO)3], Mn2+ ions (S=52) occupy the nodes of a "trillium"net. We show that the system is strongly magnetically frustrated: the Néel transition is suppressed well below the characteristic magnetic interaction strength; short-range magnetic order persists far above the Néel temperature; and the magnetic susceptibility exhibits a pseudo-plateau at 13-saturation magnetization. A simple model of nearest-neighbor Heisenberg antiferromagnetic and dipolar interactions accounts quantitatively for all observations, including an unusual 2-k magnetic ground state. We show that the relative strength of dipolar interactions is crucial to selecting this particular ground state. Geometric frustration within the classical spin liquid regime gives rise to a large magnetocaloric response at low applied fields that is degraded in powder samples as a consequence of the anisotropy of dipolar interactions.
| Original language | English |
|---|---|
| Article number | 177201 |
| Journal | Physical Review Letters |
| Volume | 128 |
| Issue number | 17 |
| DOIs | |
| State | Published - Apr 29 2022 |
Funding
The authors gratefully acknowledge financial support from the ERC (Grant 788144), EPSRC (Grant EP/T027886/1), and the Leverhulme Trust (Grant RPG-2018-268). J. A. M. P.’s work at Cambridge was supported by Churchill College, Cambridge. J. A. M. P.’s work at O. R. N. L. was supported by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT–Battelle, LLC for the U.S. Department of Energy. J. M. B. and A. L. G. gratefully acknowledge assistance from Philip Welch (Oxford). Low temperature magnetization experiments were funded by the European Union’s Horizon 2020 Research and Innovation Programme, under Grant Agreement No. 824109.