Journal of Vacuum Science & Technology A, Vol.18, No.4, 1264-1268, 2000
Exchange bias in Fe/Cr double superlattices
Utilizing the oscillatory interlayer exchange coupling in Fe/Cr superlattices, we have constructed "double superlattice" structures where a ferromagnetic (F) and an antiferromagnetic (BF) Fe/Cr superlattice are coupled through a Cr spacer. The minor hysteresis loops in the magnetization are shifted from zero field, i.e., the F superlattice is exchange biased by the AF one. The double superlattices are sputter deposited with (211) epitaxy and possess uniaxial in-plane magnetic anisotropy. The magnitude of the bias field is satisfactorily described by the classic formula for collinear spin structures. The coherent structure and insensitivity to atomic-scale roughness makes it possible to determine the spin distribution by polarized neutron reflectivity, which confirms that the spin structure is collinear. The magnetic reversal behavior of the double superlattices suggests that a realistic model of exchange bias needs to address the process of nucleating local reverse domains.