The paramagnetic-to-ferromagnetic transition in B2-structured Fe-Al single crystals: Experiments and calculations

It is well established that single crystals of B2-structured Fe-Al change from paramagnetic to ferromagnetic upon plastic deformation. This strain-induced ferromagnetism arises mostly from Fe atoms which have three or more like nearest neighbours (NNs) in antiphase-boundary (APB) tubes. Such Fe atoms carry magnetic moments according to their local environment. In this study, the saturation magnetizations, M S , of cold-rolled Fe-34 at.% Al, Fe-40 at.% Al and Fe-43 at.% Al single crystals were measured in a vibrating-sample magnetometer from 77 K to room temperature and transmission electron microscopy was used to confirm the presence of APB tubes. After magnetic measurements, rolled single crystals were heated in a differential scanning calorimeter at 20 K min m1 to 973 K and the enthalpy associated with the removal of the APB tubes measured. From the enthalpy measurement, the APB tube density and the number of Fe NNs were estimated. Hence, the M S values at 0 K were calculated. These were in good agreement with the experimentally determined values.