  The low-temperature magnetic excitations of the two-dimensional spin-5/2
square-lattice Heisenberg antiferromagnet Rb2MnF4 have been probed using pulsed
inelastic neutron scattering. In addition to dominant sharp peaks identified
with one-magnon excitations, a relatively weak continuum scattering is also
observed at higher energies. This is attributed to neutron scattering by pairs
of magnons and the observed intensities are consistent with predictions of spin
wave theory.
