  Using spin waves we directly probe the interface of an exchange biased
Ni$_{80}$Fe$_{20}$/Ir$_{25}$Mn$_{75}$ film which has been modified by the
presence of an Au dusting layer. Combining this experimental data with a
discretised simulation model, parameters relating to interface exchange
coupling and modification of interface magnetisation are determined. Exchange
coupling is found to be relatively uniform as gold thickness is increased, and
undergoes a sudden drop at 1.5$\textrm{\AA}$ of gold. Interface magnetisation
decreases as a function of the gold dusting thickness. Antiparallel alignment
of the ferromagnet and antiferromagnet supress the interface magnetisation
compared to when they are in parallel alignment. These findings imply that the
interface region has specific magnetisation states which depend on the
ferromagnet orientation.
