Neutron-scattering studies of the S = 2 antiferromagnetic chain MnCl₃(C₁₀D₈N₂)

Quasi-elastic and inelastic neutron scattering studies of the quasi-one-dimensional S = 2 antiferromagnet McCl₃(C₁₀D₈N₂) are reported. The quasi-elastic measurements exhibit a broad peak at Q ≈ 0.69 Å^-1, which is consistent with short-range antiferromagnetic coupling between neighboring Mn³⁺ ions. Inelastic experiments, at 150 mK and Q = 0.70 Å^-1, reveal decreased magnetic scattering at energies less than 0.2 meV when compared to similar studies at 20 K. These results provide microscopic evidence for the presence of a Haldane gap and are consistent with the bulk magnetization measurements of Granroth et al.