In Situ X‐Ray Absorption Studies on Local Structure of Annealed Metallic Glasses FeGaB and FeCoSiB

The microscopic structure of Fe-based metallic glasses (FeGaB) and (FeCoSiB) is investigated during in situ thermal annealing using extended X-ray absorption fine structure spectroscopy (EXAFS) above the Fe–K and Co–K absorption edges. FeGaB exhibits a phase transition above 450 °C, changing from amorphous glass to a partially crystalline structure. Its medium-range structure after this transition is modeled from crystalline α-Fe and reference structures, combined with amorphous nearest-neighbor (NN) contributions of . Local order in the glass phase is described with the same model, restricted to NN interactions. Changes in the amorphous structure occur at annealing temperatures which coincide with typical observations of changes in magnetic behavior. Meanwhile, in FeCoSiB, the EXAFS response is highly different between the Fe–K and Co–K absorption edges. EXAFS oscillations on the Fe edge are strongly suppressed, as opposed to the Co edge which shows typical amplitudes. Limited resolution in this data set allows modeling only in the first amorphous shell, based on the NN distances from FeCo. The cause of the two materials’ different EXAFS behavior at Fe–K despite similar iron content and identical experimental conditions is currently unknown and subject of further investigation.