  Standing spin waves in a thin film are used as sensitive probes of interface
pinning induced by an antiferromagnet through exchange anisotropy. Using
coplanar waveguide ferromagnetic resonance, pinning of the lowest energy spin
wave thickness mode in Ni(80)Fe(20)/Ir(25)Mn(75) exchange biased bilayers was
studied for a range of IrMn thicknesses. We show that pinning of the standing
mode can be used to amplify, relative to the fundamental resonance, frequency
shifts associated with exchange bias. The shifts provide a unique `fingerprint'
of the exchange bias and can be interpreted in terms of an effective
ferromagnetic film thickness and ferromagnet/antiferromagnet interface
anisotropy. Thermal effects are studied for ultra-thin antiferromagnetic
Ir(25)Mn(75) thicknesses, and the onset of bias is correlated with changes in
the pinning fields. The pinning strength magnitude is found to grow with
cooling of the sample, while the effective ferromagnetic film thickness
simultaneously decreases. These results suggest that exchange bias involves
some deformation of magnetic order in the interface region.
