Renormalization of spin excitations in hexagonal HoMnO3 by magnon-phonon coupling

Abstract

Hexagonal HoMnO3, a two-dimensional Heisenberg antiferromagnet, has been studied via inelastic neutron scattering. A simple Heisenberg model with a single-ion anisotropy describes most features of the spin-wave dispersion curves. However, there is shown to be a renormalization of the magnon energies located at around 11 meV. Since both the magnon-magnon interaction and magnon-phonon coupling can affect the renormalization in a noncollinear magnet, we have accounted for both of these couplings by using a Heisenberg XXZ model with 1/S expansions [1] and the Einstein site phonon model [13], respectively. This quantitative analysis leads to the conclusion that the renormalization effect primarily originates from the magnon-phonon coupling, while the spontaneous magnon decay due to the magnon-magnon interaction is suppressed by strong two-ion anisotropy.

Hybridization and Decay of Magnetic Excitations in Two-Dimensional Triangular Lattice Antiferromagnets

“…5(a). 26 There is clearly the downward curvature along the XM direction and diffusive signals above the upper magnon branch, which resemble very closely with the magneto-elastic excitation in LuMnO 3 . Unlike other RMnO 3 materials, however HoMnO 3 exhibits a very weak Mn trimerization effect, almost negligible at low temperature according to neutron diffraction studies.…”

Localized spin‐flip excitations in hexagonal HoMnO3

“…Assuming that the 760 cm ‐1 peak corresponds to the spin flip of the three Mn spins in one Mn trimer (satisfying total ∆ S z = 0), we estimate the spin exchange integral J 2 value is ~2 meV, consistent with the neutron scattering results. [ 6 ]…”

“…Among them, HoMnO 3 is an intriguing material and is widely studied because it has complex magnetic properties: magnetic ordering, [ 3 ] spin frustration, and spin–lattice coupling. [ 4–6 ]…”

Momentum-Dependent Magnon Lifetime in the Metallic Noncollinear Triangular AntiferromagnetCrB2

“…As far as these phenomena are concerned, triangular lattice antiferromagnets (TLAFs) have been at the center of active research, since they naturally host noncollinear magnetic structure due to their inherent geometrical frustration [3]. Several previous studies have demonstrated such effects in insulating TLAFs with noncollinear magnetic ground states, e.g., magnon linewidth broadening and magnetoelastic modes in hexagonal manganites RMnO 3 (R ¼ Y, Lu, Ho) [2,[4][5][6] and delafossites ACrO 2 (A ¼ Li, Cu) [7,8], and renormalization of magnons in S ¼ 1=2 TLAF Ba 3 CoSb 2 O 9 [9,10], to name only a few.…”