Magnons and electromagnons in a spin-lattice-coupled frustrated magnet CuFeO2 as seen via inelastic neutron scattering

Abstract

We have investigated spin-wave excitations in a four-sublattice (4SL) magnetic ground state of a frustrated magnet CuFeO2, in which `electromagnon' (electric-field-active magnon) excitation has been discovered by recent terahertz time-domain spectroscopy [Seki et al. Phys. Rev. Lett. 105 097207 (2010)]. In previous study, we have identified two spin-wave branches in the 4SL phase by means of inelastic neutron scattering measurements under applied uniaxial pressure. [T. Nakajima et al. J. Phys. Soc. Jpn. 80 014714 (2011) ] In the present study, we have performed high-energy-resolution inelastic neutron scattering measurements in the 4SL phase, resolving fine structures of the lower-energy spin-wave branch near the zone center. Taking account of the spin-driven lattice distortions in the 4SL phase, we have developed a model Hamiltonian to describe the spin-wave excitations. The determined Hamiltonian parameters have successfully reproduced the spin-wave dispersion relations and intensity maps obtained in the inelastic neutron scattering measurements. The results of the spin-wave analysis have also revealed physical pictures of the magnon and electromagnon modes in the 4SL phase, suggesting that collinear and noncollinear characters of the two spin-wave modes are the keys to understand the dynamical coupling between the spins and electric dipole moments in this system.

8 pages, 6 figures

References in corpus (7)

• Magnetic Interaction in the Geometrically Frustrated Triangular Lattice Antiferromagnet $\mathrm{CuFe}{\mathrm{O}}_2$
• Electric Polarization Induced by a Proper Helical Magnetic Ordering in a Delafossite Multiferroic CuFe1-xAlxO2
• Spin phonon induced colinear order and magnetization plateaus in triangular and kagome antiferromagnets. Applications to CuFeO_2
• Electromagnons in the spin collinear state of a triangular lattice antiferromagnet
• Identification of microscopic spin-polarization coupling in the ferroelectric phase of a magnetoelectric multiferroic CuFe1-xAlxO2
• The Collinear Magnetic Phases of the Geometrically-Frustrated Antiferromagnet CuFeO${}_2$: The Importance of Stacking
• Spin-Wave Spectrum in `Single-Domain' Magnetic Ground State of Triangular Lattice Antiferromagnet CuFeO2

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• Low-temperature heat transport of CuFe${}_{1-x}$Ga${}_x$O${}_2$ ($x=$ 0--0.12) single crystals
• Three dimensional magnetism and coupling to conduction electrons in PdCrO2
• Polarization memory in the nonpolar magnetic ground state of multiferroic CuFeO2
• Spin-Driven Bond Order in a 1/5-Magnetization Plateau Phase in a Triangular Lattice Antiferromagnet CuFeO2
• Rich magnetoelectric phase diagrams of multiferroic single-crystal alpha-NaFeO2