Magnetic configurations in exchange-biased double superlattices

The layer-by-layer magnetization of a “double-superlattice” Fe/Cr(211) exchange-bias junction was determined by polarized neutron reflectometry. An n-layered $[\mathrm{Fe/Cr}{]}_n$ antiferromagnetic (AF) superlattice is coupled with an m-layered $[\mathrm{Fe/Cr}{]}_m$ ferromagnetic (F) superlattice, to provide a controlled exchange bias. In low magnetic fields, the magnetizations of the two superlattices are collinear. The two magnetized states (along or opposite to the bias field) differ only in the relative orientation of the F and adjacent AF layer. At higher fields, the AF moments flop to the direction perpendicular to the applied field. The structure, thus determined, explains the magnitude of the bias field.