Fitting crystal field excitations using point-charge model -- application to rare earth pyrochlore, Kagome, and triangular magnets

ORAL

Abstract

Determining the single ion crystal field (CF) Hamiltonian is usually an indispensable step to understand the collective low-temperature magnetism in rare earth magnets. This sometimes becomes challenging in low-symmetry systems due to the limited experimental observables compared to a large number of fitted CF parameters. Here I describe a general method to fit neutron CF excitation spectrum using point charge models. By benchmarking with the existing inelastic neutron scattering measurements of pyrochlore oxides (R2X2O7), we achieve a simple and universal point-charge model. This model is then modified and applied to the newly discovered tripod Kagome magnets (R2Mg2Sb3O14), through which the principal axes and local g-tensor in the pseudo-spin basis can be determined and diagonalized. Finally, we apply the point-charge calculation to the triangular lattice magnet YbMgGaO4 and relates its mysterious extra CF levels to the local structure disorder.

*The work at Georgia Tech was sponsored by the Department of Energy under grant DE-SC-0018660. The work at U. Tennessee was supported by NSF-DMR-1350002.

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Presenters

  • Zhiling Dun

    • School of Physics, Georgia Institute of Technology
    • Georgia Institute of Technology
    • School of Physics, Georgia Tech
    • University of Tennessee
    • Department of Physics, University of Tennessee

Authors

  • Zhiling Dun

    • School of Physics, Georgia Institute of Technology
    • Georgia Institute of Technology
    • School of Physics, Georgia Tech
    • University of Tennessee
    • Department of Physics, University of Tennessee

  • Xiaojian Bai

    • School of Physics, Georgia Institute of Technology
    • Georgia Institute of Technology

  • Joseph Paddison

    • Churchill College, University of Cambridge
    • Cambridge
    • University of Cambridge
    • Georgia Institute of Technology
    • Univserity of Cambridge
    • Department of Physics, University of Cambridge

  • Matthew Brandon Stone

    • Neutron Scattering Division, Oak Ridge National Laboratory
    • Oak Ridge National Laboratory
    • Oak Ridge National Lab
    • Spallation Neutron Source, Oak Ridge National Laboratory

  • Haidong Zhou

    • University of Tennessee
    • Department of Physics and Astronomy, University of Tennessee
    • University of Tennessee, Knoxville
    • Physics, University of Tennessee, Knoxville, TN, United States
    • Physics, University of Tennessee
    • Department of Physics and Astronomy, The University of Tennessee, Knoxville
    • Department of Physics and Astronomy, University of Tennessee, Knoxville
    • Department of Physics, University of Tennessee

  • Martin Mourigal

    • School of Physics, Georgia Institute of Technology
    • Georgia Institute of Technology
    • School of Physics, Georgia Tech