Antiferromagnetism in the magnetoelectric effect single crystal LiMnPO₄

Elastic and inelastic neutron-scattering studies reveal details of the antiferromagnetic transition and intriguing spin dynamics in the magnetoelectric effect single crystal LiMnPO₄. The elastic-scattering studies confirm that the system is antiferromagnetic below T_N=33.75 K with local magnetic moments (Mn²⁺; S=5/2) that are aligned along the crystallographic a axis. The spin-wave dispersion curves propagating along the three principal axes, determined by inelastic scattering, are adequately modeled in the linear spin-wave framework assuming a spin Hamiltonian that is parametrized by inter- and in-plane nearest- and next-nearest-neighbor interactions and by easy-plane anisotropy. The temperature dependence of the spin dynamics makes this an excellent model many-body spin system to address the question of the relationship between spin-wave excitations and the order parameter.