Magnetic Excitations of the Classical Spin Liquid MgCr_{2}O_{4}

X Bai; J A M Paddison; E Kapit; S M Koohpayeh; J-J Wen; S E Dutton; A T Savici; A I Kolesnikov; G E Granroth; C L Broholm; J T Chalker; M Mourigal

doi:10.1103/PhysRevLett.122.097201

Magnetic Excitations of the Classical Spin Liquid MgCr_{2}O_{4}

Phys Rev Lett. 2019 Mar 8;122(9):097201. doi: 10.1103/PhysRevLett.122.097201.

Authors

X Bai¹, J A M Paddison^{1

2}, E Kapit^{3

4}, S M Koohpayeh⁵, J-J Wen⁵, S E Dutton⁶, A T Savici⁷, A I Kolesnikov⁷, G E Granroth⁷, C L Broholm^{5

7}, J T Chalker³, M Mourigal^{1

5}

Affiliations

¹ School of Physics, Georgia Institute of Technology, Atlanta, Georgia 30332, USA.
² Churchill College, University of Cambridge, Storey's Way, Cambridge CB3 0DS, United Kingdom.
³ Rudolf Peierls Centre for Theoretical Physics, University of Oxford, Parks Road, Oxford OX1 3NP, United Kingdom.
⁴ Department of Physics, Colorado School of Mines, Golden, Colorado 80401, USA.
⁵ Institute for Quantum Matter and Department of Physics and Astronomy, The Johns Hopkins University, Baltimore, Maryland 21218, USA.
⁶ Department of Chemistry, Princeton University, Princeton, New Jersey 08544, USA.
⁷ Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.

PMID: 30932548
DOI: 10.1103/PhysRevLett.122.097201

Abstract

We report a comprehensive inelastic neutron-scattering study of the frustrated pyrochlore antiferromagnet MgCr_{2}O_{4} 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 MgCr_{2}O_{4} 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 MgCr_{2}O_{4} is proximate to a spiral spin-liquid phase distinct from the Coulomb phase, which has implications for the magnetostructural phase transition in MgCr_{2}O_{4}.