Abstract
In this paper, we present a comprehensive study of magnetic dynamics in the rare-earth orthoferrite YbFeO3 at temperatures below and above the spin-reorientation (SR) transition TSR=7.6K, in magnetic fields applied along the a,b, and c axes. Using single-crystal inelastic neutron scattering, we observed that the spectrum of magnetic excitations consists of two collective modes well separated in energy: 3D gapped magnons with a bandwidth of ∼60meV, associated with the antiferromagnetically (AFM) ordered Fe subsystem, and quasi-1D AFM fluctuations of ∼1meV within the Yb subsystem, with no hybridization of those modes. The spin dynamics of the Fe subsystem changes very little through the SR transition and could be well described in the frame of semiclassical linear spin-wave theory. On the other hand, the rotation of the net moment of the Fe subsystem at TSR drastically changes the excitation spectrum of the Yb subsystem, inducing the transition between two regimes with magnon and spinonlike fluctuations. At T<TSR, the Yb spin chains have a well defined field-induced ferromagnetic (FM) ground state, and the spectrum consists of a sharp single-magnon mode, a two-magnon bound state, and a two-magnon continuum, whereas at T>TSR only a gapped broad spinonlike continuum dominates the spectrum. In this work we show that a weak quasi-1D coupling within the Yb subsystem JYb-Yb, mainly neglected in previous studies, creates unusual quantum spin dynamics on the low-energy scales. The results of our work may stimulate further experimental search for similar compounds with several magnetic subsystems and energy scales, where low-energy fluctuations and underlying physics could be "hidden" by a dominating interaction.
| Original language | English |
|---|---|
| Article number | 064424 |
| Journal | Physical Review B |
| Volume | 98 |
| Issue number | 6 |
| DOIs | |
| State | Published - Aug 27 2018 |
Funding
This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by Oak Ridge National Laboratory. Part of this work was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. D.S.I. acknowledges funding by the German Research Foundation (DFG) through the Collaborative Research Center SFB-1143 at the TUDresden (project C03). We would like to thank A. Sukhanov, O. Stockert, and P. Thalmeier for useful discussions. This research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by Oak Ridge National Laboratory. Part of this work was supported by the US Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division. D.S.I. acknowledges funding by the German Research Foundation (DFG) through the Collaborative Research Center SFB 1143 at the TU Dresden (project C03). S.E.N. acknowledges support from the International Max Planck Research School for Chemistry and Physics of Quantum Materials (IMPRS-CPQM). L.S.W. was supported by the Laboratory Directed Research and Development Program of Oak Ridge National Laboratory, managed by UT-Battelle, LLC, for the US DOE. S.B. and S.A.G. are supported by BFFR, Grant No. F18KI-022
| Funders | Funder number |
|---|---|
| BFFR | F18KI-022 |
| U.S. Department of Energy | |
| California Department of Fish and Game | |
| Office of Science | |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory | |
| Division of Materials Sciences and Engineering | |
| Deutsche Forschungsgemeinschaft | SFB 1143 |
| International Max Planck Research School for Chemistry and Physics of Quantum Materials |