Abstract
We report a comprehensive neutron scattering study of low energy magnetic excitations in the breathing pyrochlore helimagnetic Cu2OSeO3. Fully documenting the four lowest energy magnetic modes that leave the ferrimagnetic configuration of the "strong tetrahedra" intact (|ℏω|<13 meV), we find gapless quadratic dispersion at the Γ point for energies above 0.2 meV, two doublets separated by 1.6(2) meV at the R point, and a bounded continuum at the X point. Our constrained rigid spin cluster model relates these features to Dzyaloshinskii-Moriya (DM) interactions and the incommensurate helical ground state. Combining conventional spin wave theory with a spin cluster form factor accurately reproduces the measured equal time structure factor through multiple Brillouin zones. An effective spin Hamiltonian describing complex anisotropic intercluster interactions is obtained.
| Original language | English |
|---|---|
| Article number | 144411 |
| Journal | Physical Review B |
| Volume | 101 |
| Issue number | 14 |
| DOIs | |
| State | Published - Apr 1 2020 |
Funding
This work was supported as part of the Institute for Quantum Matter, an Energy Frontier Research Center funded by the US Department of Energy, Office of Science, Basic Energy Sciences under Award No. DE-SC0019331. C.B. and J.K. were supported by the Gordon and Betty Moore foundation under the EPIQS program Grant No. GBMF-4532. Access to MACS was provided by the Center for High Resolution Neutron Scattering, a partnership between the National Institute of Standards and Technology and the National Science Foundation under Agreement No. DMR-1508249. We wish to thank Jonathan Gaudet and Predrag Nikolic for the useful discussion on understanding the -point broadening, and Jiao Lin for helping evaluating the instrumental resolution of SEQUOIA.