Abstract
We report a comprehensive inelastic neutron-scattering study of the frustrated pyrochlore antiferromagnet MgCr2O4 in its cooperative paramagnetic regime. Theoretical modeling yields a microscopic Heisenberg model with exchange interactions up to third-nearest neighbors, which quantitatively explains all of the details of the dynamic magnetic response. Our work demonstrates that the magnetic excitations in paramagnetic MgCr2O4 are faithfully represented in the entire Brillouin zone by a theory of magnons propagating in a highly correlated paramagnetic background. Our results also suggest that MgCr2O4 is proximate to a spiral spin-liquid phase distinct from the Coulomb phase, which has implications for the magnetostructural phase transition in MgCr2O4.
Original language | English |
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Article number | 097201 |
Journal | Physical Review Letters |
Volume | 122 |
Issue number | 9 |
DOIs | |
State | Published - Mar 5 2019 |
Funding
We thank Oleg Tchernyshyov for many useful discussions during the earlier stages of this project. The work at Georgia Tech and at the Institute for Quantum Matter was supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Materials Sciences and Engineering Division under Awards No. DE-SC-0018660 and No. DE-FG02-08ER46544, respectively. The work at Oxford University was supported by the EPSRC under Grant No. EP/I032487/1. The research at Oak Ridge National Laboratory's Spallation Neutron Source was sponsored by the U.S. Department of Energy, Office of Basic Energy Sciences, Scientific User Facilities Division. J.?A.?M.?P. acknowledges financial support from Churchill College, Cambridge (UK). C.?B. was supported by the Gordon and Betty Moore foundation under GBMF 4532. M.?M. and J.?T.?C. acknowledge the Kavli Institute for Theoretical Physics (KITP) where part of this research was started. KITP is supported by the National Science Foundation under Grant No. NSF-PHY-1748958.