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Title: Electromagnon excitation in the field-induced nonlinear ferrimagnetic phase of Ba2Mg2Fe12O22 studied by polarized inelastic neutron and terahertz time-domain optical spectroscopy

We have studied magnetic excitations in a field-induced noncollinear commensurate ferrimagnetic phase of Ba2Mg2Fe12O22 by means of polarized inelastic neutron scattering (PINS) and terahertz (THz) time-domain optical spectroscopy under magnetic field. A previous THz spectroscopy study reported that the field-induced phase exhibits electric-dipole-active excitations with energies of around 5 meV [Kida et al., Phys. Rev. B 83, 064422 (2011)]. In the present PINS measurements, we observed inelastic scattering signals around 5 meV at the zone center in the spin-flip channel. This directly shows that the electric-dipole-active excitations are indeed of magnetic origin, that is, electromagnons. In addition, the present THz spectroscopy confirms that the excitations have oscillating electric polarization parallel to the c axis. In terms of the spin-current model (Katsura-Nagaosa-Balatsky model), the noncollinear magnetic order in the field-induced phase can induce static electric polarization perpendicular to the c axis, but not dynamic electric polarization along the c axis. Furthermore, we suggest that the electromagnon excitations can be explained by applying the magnetostriction model to the out-of-phase oscillations of the magnetic moments, which is deduced from the present experimental results.
 [1] ;  [2] ;  [3] ;  [4] ;  [5] ;  [3] ;  [1] ;  [6] ;  [7]
  1. RIKEN Center for Emergent Matter Science (CEMS), Saitama (Japan)
  2. Univ. of Tokyo, Tokyo (Japan); Japan Science and Technology Agency, Tokyo (Japan)
  3. Univ. of Tokyo, Tokyo (Japan)
  4. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)
  5. RIKEN Center for Emergent Matter Science (CEMS), Saitama (Japan); Japan Atomic Energy Agency, Ibaraki (Japan)
  6. RIKEN Center for Emergent Matter Science (CEMS), Saitama (Japan); Univ. of Tokyo, Tokyo (Japan)
  7. RIKEN Center for Emergent Matter Science (CEMS), Saitama (Japan); Univ. of Tokyo, Kashiwa (Japan)
Publication Date:
OSTI Identifier:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Physical Review B
Additional Journal Information:
Journal Volume: 93; Journal Issue: 3; Journal ID: ISSN 2469-9950
American Physical Society (APS)
Research Org:
Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). High Flux Isotope Reactor (HFIR)
Sponsoring Org:
USDOE Office of Science (SC)
Country of Publication:
United States