We have investigated the evolution of magnetic properties as we grow FexMn1–x alloys on 25 ML thick Ni/Cu(100) films. We have choosen these Ni films since they exhibit a perpendicular magnetization. Along this direction we were able to detect magnetic signals of fcc FexMn1–x/Cu(100) as previously reported. We find that the polar Kerr intensity initially increases during FexMn1–x alloy growth on 25 ML Ni. It peaks at ∼2 ML where we observe 1.4 times the Kerr signal of 25 ML Ni. This enhancement is equivalent to the signal of 1 ML Fe it also compares nicely with the signal levels on FexMn1–x/Cu(100) films. Upon further deposition the signal decreases and finally returns to the value of the bare Ni film at ∼3.5 ML.Reversing the deposition order allows us to study the effect on the Spin Reorientation Transition (SRT) of Ni films. We find that the reorientation thickness dc increases by ∼3 ML if the substrate is changed from Cu(100) to Fe50Mn50.