Magnetic excitations in the spin-52 antiferromagnetic trimer substance SrMn ₃P ₄O ₁₄

A quantum-mechanical 1/3 magnetization plateau and magnetic long-range order appear in the large-spin (5/2) substance SrMn ₃P ₄O ₁₄. Previous magnetization results suggest that the spin system consists of antiferromagnetic trimers that are weakly coupled with one another. We inferred that the magnetization plateau originated from discrete energy levels of the trimer. In order to confirm the discrete energy levels, we performed inelastic neutron-scattering experiments on SrMn ₃P ₄O ₁₄ powders. Observed magnetic excitations are consistent with excitations expected in the trimer model.