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Renormalization of spin excitations in hexagonal HoMnO3 by magnon-phonon coupling
Kim, Taehun,Leiner, Jonathan C.,Park, Kisoo,Oh, Joosung,Sim, Hasung,Iida, Kazuki,Kamazawa, Kazuya,Park, Je-Geun American Physical Society 2018 Physical review. B Vol.97 No.20
<P>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.</P>
Park, Kisoo,Oh, Joosung,Leiner, Jonathan C.,Jeong, Jaehong,Rule, Kirrily C.,Le, Manh Duc,Park, Je-Geun American Physical Society 2016 Physical Review B Vol.94 No.10
<P>CuCrO2 is a manifestation of a two-dimensional triangular antiferromagnet which exhibits an incommensurate noncollinear magnetic structure similar to a classical 120 degrees. ordering. Using the inelastic neutron scattering technique, direct evidence of a magnon-phonon coupling in CuCrO2 is revealed via the mixed magnon-phonon character of the excitation mode at 12.5 meV as well as a minimum at the zone boundary. A simple model Hamiltonian that incorporates an exchange-striction type magnon-phonon coupling accurately reproduces the observed features. Also, continuum excitations originating from the interaction between quasiparticles are observed with strong intensity at the zone boundary. These features of the magnetic excitations are key to an understanding of the emergent excitations in noncollinear antiferromagnetic compounds.</P>
Low-energy spin dynamics of orthoferrites AFeO<sub>3</sub> (A = Y, La, Bi)
Park, Kisoo,Sim, Hasung,Leiner, Jonathan C,Yoshida, Yoshiyuki,Jeong, Jaehong,Yano, Shin-ichiro,Gardner, Jason,Bourges, Philippe,Klicpera, Milan,Sechovský,, Vladimí,r,Boehm, Martin,Park, Je IOP 2018 Journal of physics, an Institute of Physics journa Vol.30 No.23
<P>YFeO<SUB>3</SUB> and LaFeO<SUB>3</SUB> are members of the rare-earth orthoferrites family with <I>Pbnm</I> space group. Using inelastic neutron scattering, the low-energy spin excitations have been measured around the magnetic Brillouin zone center. Splitting of magnon branches and finite magnon gaps (∼2 meV) are observed for both compounds, where the Dzyaloshinsky–Moriya interactions account for most of this gap with some additional contribution from single-ion anisotropy. We also make comparisons with multiferroic BiFeO<SUB>3</SUB> (<I>R3c</I> space group), in which similar behavior was observed. By taking into account all relevant local Dzyaloshinsky–Moriya interactions, our analysis allows for the precise determination of all experimentally observed parameters in the spin-Hamiltonian. We find that different properties of the <I>Pbnm</I> and <I>R3c</I> space group lead to the stabilization of a spin cycloid structure in the latter case but not in the former, which explains the difference in the levels of complexity of magnon band structures for the respective compounds.</P>