The perpendicular unidirectional anisotropy constant, J K perp, of Mn-Ir/Fe-Co/[Pt/Co] 4 multilayers was investigated by systematically changing the Fe-Co layer composition, and was compared with the in-plane unidirectional anisotropy constant, J K in, of Mn-Ir/Fe-Co bilayers. Observed trends were similar for the variation of J K perp and J K in against the compositional change. This result indicates that the perpendicular exchange anisotropy and in-plane exchange anisotropy are induced by similar mechanisms. On the other hand, an apparent discrepancy was pointed out between the absolute values of J K perp and J K in in particular for the compositional region where Fe-Co forms body-centered-cubic (bcc) structure. This significant discrepancy in the bcc-Fe-Co region was explained by the magnetic anisotropy of the Fe-Co layer, and it is expected that J K perp could be increased as large as J K in when strong perpendicular magnetic anisotropy is induced in the Fe-Co layer.
- Compositional dependence
- Exchange bias
- Perpendicular exchange anisotropy
- Perpendicular magnetic anisotropy