Oscillatory interlayer exchange coupling in Ni81Fe19/Cu/Ni81Fe19Fe50Mn50 spin valves

An oscillatory behavior is observed in the indirect exchange coupling between the two ferromagnetic layers in sputtered (111) and (100) Ni81Fe19/Cut(Cu)/Ni81Fe19/Fe50Mn50 spin valves. The periods of oscillations are 13.5 and 12.5 Angstrom for the (111) and (100) growth directions, respectively. The coupling changes from strongly ferromagnetic, at t(Cu) 12 Angstrom, to antiferromagnetic at t(Cu) = 9.5 Angstrom. At the transition region where the bilinear coupling changes sign (t(Cu) approximate to 10 Angstrom) biquadratic coupling is observed. The amplitude of the giant magnetoresistive effect reaches its maximum value for t(Cu) = 12 Angstrom, and values in excess of 4% are still observed for t(Cu) = 10 Angstrom. 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. (C) 1996 American Institute of Physics.