Magnetic ordering in Fe/Mn superlattices

The atomic structure and magnetic properties of Fe/Mn superlattices are presented. X-ray diffraction and modelling have been performed, and the Fe/Mn superlattices are found to have atomically flat interfaces, with the Mn stabilised in the body-centred tetragonal structure. We have studied the ordering of the ferromagnetic Fe blocks. Either an antiferromagnetic, ferromagnetic or non-colinear magnetic structure is found, depending on Mn thickness. The antiferromagnetic ordering of the Mn has been studied by neutron diffraction in a superlattice of composition [Fe(12A)/Mn(6A)]300. A totally unexpected magnetic structure is obtained, with Mn moments perpendicular to those of Fe. On the basis of these results, the simple antiferromagnetic ordering assumed for other exchange-biased systems should, therefore, be reconsidered