We present a magneto-optical Kerr effect study of epitaxial bilayers consisting of Ni and NixMn1−x on Cu3Au(001). The bottom Ni layer, the NixMn1−x layer thickness and its chemical composition were changed and the Curie temperature of the system was determined. We focused on two different regimes of NixMn1−x composition, namely a Mn-rich with x between 0.25 and 0.5, and a Ni-rich with x around 0.7. In these two composition ranges, a NixMn1−x overlayer exhibits a different effect on the Curie temperature of the Ni layer. While Mn-rich NixMn1−x layers reduce the Curie temperature of the Ni underlayer, Ni-rich NixMn1−x layers enhance the Curie temperature with respect to the pure Ni film. This is attributed to changes in the effective thickness of the Ni layer by exchange interactions with the NixMn1−x overlayer.
