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Thygesen PM, Paddison JA, Zhang R, et al. Orbital Dimer Model for the Spin-Glass State in Y_{2}Mo_{2}O_{7}. Phys Rev Lett. 2017;118(6):067201doi: 10.1103/PhysRevLett.118.067201.
Thygesen, P. M., Paddison, J. A., Zhang, R., Beyer, K. A., Chapman, K. W., Playford, H. Y., Tucker, M. G., Keen, D. A., Hayward, M. A., & Goodwin, A. L. (2017). Orbital Dimer Model for the Spin-Glass State in Y_{2}Mo_{2}O_{7}. Physical review letters, 118(6), 067201. https://doi.org/10.1103/PhysRevLett.118.067201
Thygesen, Peter M M, et al. "Orbital Dimer Model for the Spin-Glass State in Y_{2}Mo_{2}O_{7}." Physical review letters vol. 118,6 (2017): 067201. doi: https://doi.org/10.1103/PhysRevLett.118.067201
Thygesen PM, Paddison JA, Zhang R, Beyer KA, Chapman KW, Playford HY, Tucker MG, Keen DA, Hayward MA, Goodwin AL. Orbital Dimer Model for the Spin-Glass State in Y_{2}Mo_{2}O_{7}. Phys Rev Lett. 2017 Feb 10;118(6):067201. doi: 10.1103/PhysRevLett.118.067201. Epub 2017 Feb 08. PMID: 28234510.
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Phys Rev Lett. 2017 Feb 10;118(6):067201. doi: 10.1103/PhysRevLett.118.067201. Epub 2017 Feb 08.

Orbital Dimer Model for the Spin-Glass State in Y_{2}Mo_{2}O_{7}.

Physical review letters

Peter M M Thygesen, Joseph A M Paddison, Ronghuan Zhang, Kevin A Beyer, Karena W Chapman, Helen Y Playford, Matthew G Tucker, David A Keen, Michael A Hayward, Andrew L Goodwin

Affiliations

  1. Department of Chemistry, University of Oxford, South Parks Road, Oxford OX1 3QR, United Kingdom.
  2. ISIS Facility, Rutherford Appleton Laboratory, Harwell Campus, Didcot, Oxfordshire OX11 0QX, United Kingdom.
  3. School of Physics, Georgia Institute of Technology, 837 State Street, Atlanta, Georgia 30332-0430, USA.
  4. Advanced Photon Source, Argonne National Laboratory, Argonne, Illinois 60439, USA.
  5. Diamond Light Source, Chilton, Oxfordshire OX11 0DE, United Kingdom.
  6. Spallation Neutron Source, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.

PMID: 28234510 DOI: 10.1103/PhysRevLett.118.067201

Abstract

The formation of a spin glass generally requires that magnetic exchange interactions are both frustrated and disordered. Consequently, the origin of spin-glass behavior in Y_{2}Mo_{2}O_{7}-in which magnetic Mo^{4+} ions occupy a frustrated pyrochlore lattice with minimal compositional disorder-has been a longstanding question. Here, we use neutron and x-ray pair-distribution function (PDF) analysis to develop a disorder model that resolves apparent incompatibilities between previously reported PDF, extended x-ray-absorption fine structure spectroscopy, and NMR studies, and provides a new and physical explanation of the exchange disorder responsible for spin-glass formation. We show that Mo^{4+} ions displace according to a local "two-in-two-out" rule on each Mo_{4} tetrahedron, driven by orbital dimerization of Jahn-Teller active Mo^{4+} ions. Long-range orbital order is prevented by the macroscopic degeneracy of dimer coverings permitted by the pyrochlore lattice. Cooperative O^{2-} displacements yield a distribution of Mo-O-Mo angles, which in turn introduces disorder into magnetic interactions. Our study demonstrates experimentally how frustration of atomic displacements can assume the role of compositional disorder in driving a spin-glass transition.

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