Ultrathin Ni films in Cu/Ni/Cu(001) bilayers and exchange coupled Ni films
in Ni/Cu/Ni/Cu(001) trilayers are investigated by magnetization induced sec
ond harmonic generation (MSHG). The results are analyzed in a model of loca
lized nonlinear polarizabilities at the interfaces. We show that antiferrom
agnetic coupling in the Ni/Cu/Ni trilayers is observable with MSHG due to t
he presence of quantum well states (QWS's) in the Cu layer. The influence o
f the QWS's on the SHG from a Ni film in a Cu/Ni/Cu(001) bilayer is weaker
compared to the case of Fe or Co bilayers.