Oscillatory exchange bias in Fe/Cr double superlattices

Abstract In the [Fe/Cr]AF/Crx/[Fe/Cr]F double superlattices consisting of a ferromagnetic Fe/Cr superlattice on top of an antiferromagnetic Fe/Cr superlattice, the exchange coupling between the superlattices is determined by the thicknesses (x) of the Cr spacer layer. The oscillating behavior of the exchange bias field of a series of (2 1 1)-oriented Fe/Cr double superlattices was determined by superconducting quantum interference device (SQUID) and magneto-optic Kerr effect (MOKE) measurements. For x >13 A a negative strongly oscillating character of the exchange bias was observed. At very thick x the exchange bias vanishes. The most immediate result is the fact that the exchange bias field is always negative, regardless of the sign of the coupling between the ferromagnetic and the antiferromagnetic superlattices. The detailed dependence of the exchange bias field as a function of the intersuperlattice thickness of Cr is explained in terms of the interaction between the two superlattices in collinear configuration.