Abstract
We present a comprehensive neutron scattering study of the breathing pyrochlore magnet LiGaCr4S8. We observe an unconventional magnetic excitation spectrum with a separation of high- and low-energy spin dynamics in the correlated paramagnetic regime above a spin-freezing transition at 12(2) K. By fitting to magnetic diffuse-scattering data, we parametrize the spin Hamiltonian. We find that interactions are ferromagnetic within the large and small tetrahedra of the breathing pyrochlore lattice, but antiferromagnetic further-neighbor interactions are also essential to explain our data, in qualitative agreement with density-functional-theory predictions [Ghosh et al., npj Quantum Mater. 4, 63 (2019)2397-464810.1038/s41535-019-0202-z]. We explain the origin of geometrical frustration in LiGaCr4S8 in terms of net antiferromagnetic coupling between emergent tetrahedral spin clusters that occupy a face-centered-cubic lattice. Our results provide insight into the emergence of frustration in the presence of strong further-neighbor couplings, and a blueprint for the determination of magnetic interactions in classical spin liquids.
| Original language | English |
|---|---|
| Article number | 167201 |
| Journal | Physical Review Letters |
| Volume | 125 |
| Issue number | 16 |
| DOIs | |
| State | Published - Oct 2020 |
Funding
We thank C. Batista for useful discussions and Gerald Morris for technical support with muon spin resonance measurements. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. G. P. and H. S. A. were partially supported by the Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant No. GBMF4416. J. A. M. P. acknowledges financial support from Churchill College, University of Cambridge, during early stages of this project. This research used resources at the Spallation Neutron Source and the High Flux Isotope Reactor, Department of Energy Office of Science User Facilities operated by Oak Ridge National Laboratory. We thank C. Batista for useful discussions and Gerald Morris for technical support with muon spin resonance measurements. This work was supported by the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. G.P. and H.S.A. were partially supported by the Gordon and Betty Moore Foundation’s EPiQS Initiative through Grant No. GBMF4416. J.A.M.P. acknowledges financial support from Churchill College, University of Cambridge, during early stages of this project. This research used resources at the Spallation Neutron Source and the High Flux Isotope Reactor, Department of Energy Office of Science User Facilities operated by Oak Ridge National Laboratory.
| Funders | Funder number |
|---|---|
| U.S. Department of Energy | |
| Gordon and Betty Moore Foundation | GBMF4416 |
| Office of Science | |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory | |
| Division of Materials Sciences and Engineering | |
| Churchill College, University of Cambridge |