We present a combined experimental and computational study of high-temperature magnetic properties of Fe-Cr alloys with chromium content up to about 20 at.%. Magnetic Cluster Expansion method is applied to model the magnetic properties of random Fe-Cr alloys, and in particular the Curie transition temperature, as functions of alloy composition. We find that at low (3-6 at. %) Cr content the Curie temperature increases as a function of Cr concentration. It is maximum at approximately 6 at. % Cr and then decreases for higher Cr content. The same feature is found in thermo-magnetic measurements performed on model Fe-Cr alloys, where a 5 at.% Cr alloy has a higher Curie temperature than pure Fe. The Curie temperatures of 10 and 15 at.% Cr alloys are found to be lower than the Curie temperature of pure Fe.
