Identification of the Curie point in Fe-based metallic glasses using in situ hard x-ray diffraction

In situ temperature-resolved x-ray diffraction was used to follow structural changes of amorphous Fe(73.5−x)Mn x Si13.5Cu1Nb3B9 (x = 1, 3, 5, 7 and 9) during constant rate heating experiments. Analysing diffraction patterns in reciprocal space by tracing the position of the first sharp diffraction peak provided information about the thermal expansion behaviour on atomic scale. Two distinct zones showing different slopes were identified for all expansion curves in the temperature range between 40 and 450 °C. The temperatures at which the expansion curves change their slopes are in good accordance with the Curie temperatures determined from thermomagnetic curves. Therefore, it is concluded that the in situ high-energy x-ray diffraction enables detection of the transition from a ferromagnetic to a paramagnetic state in the case of Fe-based metallic glasses.