Interface coupling and magnetic properties of exchange-coupled Ni₈₁Fe₁₉/Ir₂₂Mn₇₈ bilayers

Hysteresis loop measurements using magnetooptic Kerr effect magnetometry in the low frequency region and magnetization dynamics measurements using high frequency permeametry are carried out to study the exchange anisotropy in Ni₈₁Fe₁₉/Ir₂₂Mn₇₈ bilayers. These two measurement techniques provide different exchange anisotropies for bilayers with thin Ir₂₂Mn₇₈ films. The observations can be understood by assuming that the AF grains break into domains due to the interface random field. By analysing the results from these two techniques, the interface coupling strength and the magnetic properties of the bilayers can be quantitatively determined.