  Inelastic neutron scattering with high wave-vector resolution has
characterized the propagation of transverse spin wave modes near the
antiferromagnetic zone center in the metastable domain state of a random field
Ising magnet. A well-defined, long wavelength excitation is observed despite
the absence of long-range magnetic order. Direct comparisons with the spin wave
dispersion in the long-range ordered antiferromagnetic state reveal no
measurable effects from the domain structure. This result recalls analogous
behavior in thermally disordered anisotropic spin chains but contrasts sharply
with that of the phonon modes in relaxor ferroelectrics.
