Spin Phonon Coupling in Hexagonal MultiferroicYMnO3

Abstract

Inelastic neutron scattering measurements have been performed on YMnO3, aiming to study the interplay between spin and lattice degrees of freedom in this hexagonal multiferroic material. Our study provides evidence for a strong coupling between magnons and phonons, evidenced by the opening of a gap below T(N) in the dispersion of the transverse acoustic phonon mode polarized along the ferroelectric axis. The resulting upper phonon branch is found to lock on one of the spin-wave modes. These findings are discussed in terms of a possible hybridization between the two types of elementary excitations.

Phonons and hybrid modes in the high and low temperature far infrared dynamics of hexagonal TmMnO3

“…8 (a)) where, although not having substructure, it is also associated with zone center magnons. [37] The TA gap opening is symmetry dependent on spin and phonon dispersions and only when there is band crossing as in YMnO 3 [17] Our results presents another view of a second order transition in strongly correlated oxides for which the long-range macroscopic view given by Xray patterns, and described by a lattice space group, is not required to change.…”

“…hybridized split band at 12 K (square) as it compares to the neutron profile (dot-bar) for the same excitation at q=0.15 in YMnO 3 [17]. Dashed lines are a two gaussian fit to this data by [17].…”

“…In this fashion one is able to trace, as in YMnO 3 , [17] through the THz peak temperature dependence (Fig. 9) the opening of the transverse acoustical phonon gap at about T N showing that the perturbation introduced at finite q by the strong coupling between phonon and spin waves results for TmMnO 3 in distinct zone center hybrids.…”

“…The phonon dispersion is polarized along the ferroelectric axis c. [17] The magnon-phonon coupling creates hybridized quasiparticles revealing a common channel for antiferromagnetism and polar order. We found, that the infrared band splitting of TmMnO 3 at ~50 cm -1 (~6 meV) agrees with the hybridized mode magnon-acoustic phonon anomaly.…”

The Magnetic Phase Transition and Universality Class of h-YMnO3 and h-(Y0.98Eu0.02)MnO3 Under Zero and Applied Pressure

“…These compounds are type-I multiferroics for R, namely, Sc, Y, Ho Er, Tm, Yb and Lu [6,7]. The results presented in this paper concern the hexagonal magnanite h-YMnO 3 (YMO), which has only one type of magnetic ion and is the most studied rare-earth manganite.…”