Magnetic Structure of Cr in Exchange Coupled Fe/Cr(001) Superlattices

Abstract

We demonstrate how the noncollinear exchange coupling between the Fe layers in Fe/Cr(001) superlattices is caused by a frustrated spiral modulation of the Cr moments not observed in bulk. The noncollinear coupling vanishes above the N\'eel temperature of this commensurate antiferromagnetic Cr order. This clarifies the essential contribution of Cr ordering to the coupling in the regime of smallest thicknesses where no incommensurate Cr spin density wave can form. For larger Cr thicknesses we observe a predicted incommensurate to commensurate transition with temperature.