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

スピンー格子結合系フラストレーション磁性体CuFeOにおけるマグノン及びエレクトロマグノンの中性子非弾性散乱による研究

中島 多朗*; 須能 梓*; 満田 節生*; 寺田 典樹*; 木村 尚次郎*; 金子 耕士   ; 山内 宏樹   

Nakajima, Taro*; Suno, Azusa*; Mitsuda, Setsuo*; Terada, Noriki*; Kimura, Shojiro*; Kaneko, Koji; Yamauchi, Hiroki

We have investigated spin-wave excitations in a four-sublattice (4SL) magnetic ground state of a frustrated magnet CuFeO, in which "electromagnon" excitation has been discovered by recent terahertz time-domain spectroscopy. 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. 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.