J A M Paddison, P Mukherjee, X Bai, Z L Dun, C R Wiebe, H D Zhou, J S Gardner, M Mourigal, and S E Dutton, Modeling Spin Dynamics in the Singlet Ground State Garnet Ho_{3}Ga_{5}O_{12}, arXiv:1908.0353021 (2019)

Materials containing non-Kramers magnetic ions can show unusual quantum excitations because of the exact mapping of the two-singlet crystal-field ground state to a quantum model of Ising spins in a transverse magnetic field. Here, we model the magnetic excitation spectrum of garnet-structured Ho_{3}Ga_{5}O_{12}, which has a two-singlet crystal-field ground state. We use a reaction-field approximation to explain published inelastic neutron-scattering data [Zhou *et al*., *Phys. Rev. B* **78**, 140406(R) (2008)] using a three-parameter model containing the magnetic dipolar interaction, the two-singlet crystal-field splitting, and the nuclear hyperfine coupling. Our study clarifies the magnetic Hamiltonian of Ho_{3}Ga_{5}O_{12}, reveals that the nuclear hyperfine interaction drives magnetic ordering in this system, and provides a framework for quantitative analysis of magnetic excitation spectra of materials with singlet crystal-field ground states.