Spin dynamics in linear magnetoelectric material Mn_3Ta_2O_8

We performed inelastic neutron scattering experiments on single crystal samples of a linear magnetoelectric material Mn_3Ta_2O_8, which exhibits a collinear antiferromagnetic order, to reveal the spin dynamics. Numerous modes observed in the neutron spectra were reasonably reproduced by linear spin-wave theory on the basis of the spin Hamiltonian including eight Heisenberg interactions and an easy-plane type single-ion anisotropy. The presence of strong frustration was found in the identified spin Hamiltonian.