Cluster Frustration in the Breathing Pyrochlore Magnet LiGaCr4S8

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 fi...

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Bibliographic Details
Published in:Physical review letters 2020-10, Vol.125 (16)
Main Authors: Pokharel, Ganesh, Arachchige, Hasitha Suriya, Williams, Travis J., May, Andrew F., Fishman, Randy S., Sala, Gabriele, Calder, Stuart, Ehlers, Georg, Parker, David S., Hong, Tao, Wildes, Andrew, Mandrus, David, Paddison, Joseph A. M., Christianson, Andrew D.
Format: Article
Language:English
Subjects:
Exchange interaction
Exotic phases of matter
Magnetic order
Magnetic phase transitions
Magnetic susceptibility
Magnetism
PHYSICS OF ELEMENTARY PARTICLES AND FIELDS
Spin dynamics
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Summary: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)]. 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.
ISSN:0031-9007
1079-7114
DOI:10.1103/PhysRevLett.125.167201