Direct method for qualitative assessment of the fraction of ordered and disordered phases in thick FePt films

• Impact of the Pt content on thick FePt films.
• Direct method for assessing the fraction of A1 and L10 phases.
• Greater sensitivity to assess the fraction of A1 and L10 phases.
• Direct evidence of the Curie temperature reduction in both phases.

The effect of the Pt content on the ordering process occurring in thick FePt films between the disordered γ(A1) and ordered γ2(L10) phases has been investigated. The in situ high temperature susceptibility measurements show two distinct magnetic signatures during this A1→L10A1→L10 transition. These results provide a qualitative method to assess the fraction of ordered and disordered phases in the samples after a given heat treatment. It also shows direct evidence of the Curie temperature reduction in both phases when the Pt content increases.