Exchange-bias effect in Fe/Cr(211) double superlattice structures

Abstract

Shifted hysteresis loops characteristic of the exchange-bias effect between a ferromagnet (F) and an antiferromagnet (AF) are demonstrated in “double-superlattice” structures. Utilizing the well-established oscillatory interlayer exchange coupling in Fe/Cr, we have constructed $[\mathrm{F}\mathrm{e}/\mathrm{C}\mathrm{r}{]}^{\mathrm{AF}}/\mathrm{C}\mathrm{r}/[\mathrm{F}\mathrm{e}/\mathrm{C}\mathrm{r}{]}^F$ double superlattices where Fe/Cr superlattices with appropriate Cr-spacer thickness represent the F and the AF. The double superlattices are (211)-oriented epitaxial films sputter grown on single-crystal MgO(110) substrates. The AF/F interface is coherent compared to conventional exchange-bias interfaces consisting of dissimilar AF and F phases. Magnetization results show that AF/F exchange coupling affects the nucleation of reverse magnetic domains, and that the magnitude of the exchange-bias field is given directly by the classic formula for collinear spin structures. The collinear spin distribution is confirmed by polarized neutron reflectivity.