Diffusion of solitons in the antiferromagnetic chains of (${\mathrm{CD}}_3$${)}_4$${\mathrm{NMnCl}}_3$: A study by neutron spin echo

Quasi one-dimensional magnetic compounds have given good examples of soliton excitations. We present new results on soliton dynamics obtained by the neutron-spin-echo method. This technique allowed a unique accurate line-shape analysis of the antiferromagnetic mode (centered at q=π/a in reciprocal space) in the time domain 0.02–1.7 nsec. Thus we could directly probe the antiferromagnetic short-range order in the chains. The analysis of the relaxation line shape of this order in (${\mathrm{CD}}_3$ ${)}_4$ ${\mathrm{NMnCl}}_3$ doped with copper reveals an exp (- √t ) time decay—a signature of diffusive soliton dynamics—and does not show the conventional exp(-t) decay expected for ballistic solitons.