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Cluster Frustration in the Breathing Pyrochlore Magnet LiGaCr4S8

Ganesh Pokharel, Hasitha Suriya Arachchige, Travis J. Williams, Andrew F. May, Randy S. Fishman, Gabriele Sala, Stuart Calder, Georg Ehlers, David S. Parker, Tao Hong, Andrew Wildes, David Mandrus, Joseph A. M. Paddison, and Andrew D. Christianson
Phys. Rev. Lett. 125, 167201 – Published 16 October 2020
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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)]. 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.

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  • Received 21 February 2020
  • Accepted 31 August 2020

DOI:https://doi.org/10.1103/PhysRevLett.125.167201

© 2020 American Physical Society

Physics Subject Headings (PhySH)

Condensed Matter, Materials & Applied Physics

Authors & Affiliations

Ganesh Pokharel1,2,*, Hasitha Suriya Arachchige1,2, Travis J. Williams3, Andrew F. May2, Randy S. Fishman2, Gabriele Sala3, Stuart Calder3, Georg Ehlers4, David S. Parker2, Tao Hong3, Andrew Wildes5, David Mandrus6,2,1, Joseph A. M. Paddison2,†, and Andrew D. Christianson2,‡

  • 1Department of Physics & Astronomy, University of Tennessee, Knoxville, Tennessee 37996, USA
  • 2Materials Science & Technology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 3Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 4Neutron Technologies Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA
  • 5Institut Laue-Langevin, CS 20156, 38042 Grenoble Cédex 9, France
  • 6Department of Materials Science & Engineering, University of Tennessee, Knoxville, Tennessee 37996, USA

  • *gpokhare@vols.utk.edu
  • paddisonja@ornl.gov
  • christiansad@ornl.gov

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Issue

Vol. 125, Iss. 16 — 16 October 2020

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