Evidence for an electric-dipole active continuum band of spin excitations in multiferroic TbMnO3.
The wide range optical spectra on a multiferroic prototype TbMnO3 have been investigated to clarify the origin of spin excitations observed in the far-infrared region. We elucidate the full band structure, whose high energy edge (133 cm;{-1}) exactly corresponds to twice of the highest-lying magnon energy. Thus the origin of this absorption band is clearly assigned to two-magnon excitation driven by the electric field of light. There is an overlap between the two-magnon and phonon energy ranges, where the strong coupling between them is manifested by the frequency shift and transfer of oscillator strength of the phonon mode.
Takahashi
Y
Y
Multiferroics Project, ERATO, Japan Science and Technology Agency (JST), Japan c/o Department of Applied Physics, The University of Tokyo, Tokyo 113-8656, Japan.
Kida
N
N
Yamasaki
Y
Y
Fujioka
J
J
Arima
T
T
Shimano
R
R
Miyahara
S
S
Mochizuki
M
M
Furukawa
N
N
Tokura
Y
Y