Oscillatory exchange bias in Fe/Cr double superlattices

In the [Fe/Cr](AF)/Cr-x/[Fe/Cr](F) double superlattices consisting of a fer romagnetic Fe/Cr superlattice on top of an antiferromagnetic Fe/Cr superlat tice, the exchange coupling between the superlattices is determined by the thicknesses (x of the Cr spacer layer. The oscillating behavior of the exch ange bias field of a series of (211)-oriented Fe/Cr double superlattices wa s determined by superconducting quantum interference device (SQUID) and mag neto-optic Kerr effect (MOKE) measurements. For x > 13 Angstrom a negative strongly oscillating character of the exchange bias was observed. At very t hick x the exchange bias vanishes. The most immediate result is the fact th at the exchange bias field is always negative, regardless of the sign of th e coupling between the ferromagnetic and the antiferromagnetic superlattice s. 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. (C) 2001 Elsevier Science B.V. All rights reserved.