For Fusion energy applications FeCr ferritic martensitic steels are candidate structural materials due to their radiation resistance and good mechanical properties. The understanding of the neutron irradiation effects on FeCr steels is of paramount importance for the development of radiation resistance materials. The damage induced in the material by fusion neutrons can be imitated employing self-ion irradiation. Polarised Neutron Reflectivity provides a unique tool to understand the changes of the magnetic state of FeCr magnetism in Fe+ ion irradiated films which is an important ingredient in the radiation damage understanding and in the development of theoretical modelling.