An oscillatory behavior is observed in the indirect exchange coupling between the two ferromagnetic layers in sputtered ⟨111⟩ and ⟨100⟩ Ni81Fe19/Cu tCu/Ni81Fe19/Fe50Mn50spin valves. The periods of oscillations are 13.5 and 12.5 A˚ for the ⟨111⟩ and ⟨100⟩ growth directions, respectively. The coupling changes from strongly ferromagnetic, attCu=12 A˚, to antiferromagnetic attCu=9.5 A˚. At the transition region where the bilinear coupling changes sign (tCu≊10 A˚) biquadratic coupling is observed. The amplitude of the giant magnetoresistive effect reaches its maximum value fortCu=12 A˚, and values in excess of 4% are still observed fortCu=10 A˚. Interface sharpness is shown to be a key parameter for the observation of antiferromagnetic coupling, as well as a large magnetoresistive effect, at very thin copper layers. ©1996 American Institute of Physics.