The structural and magnetic properties of rapidly solidified Fe100−xGax alloys, for 12.8≤x≤27.5

Abstract

This work presents the findings from structural, magnetic, and thermal investigations of melt-spun ribbons of Fe100−xGax alloys where 12.8≤x≤27.5at%. X-ray diffraction analysis from the as-spun samples indicates that all of the compositions form the disordered bcc A2 phase. Thermo-magnetic observations of the Fe-rich compositions where x=12.8, 17.5 and 19.5 show temperature dependent magnetisation curves where the A2 bcc phase is retained through the heating and cooling cycles. However, the compositions of x=22.5 and 27.5 both show anomalies, where a marked increase in magnetisation is detected at high temperatures indicating a substantial structural reconfiguration. Repetition of these measurements confirm that both structural and magnetic hysteresis occurs in both these compositions; however, in the x=22.5 composition these changes are eventually removed but not so for the x=27.5 sample. Repetitive thermal measurements using differential scanning calorimetry of the x=27.5 sample coupled with direct comparison to the thermo-magnetic measurements ascertain excellent evidence for the structural and magnetic transitions that are observed. In agreement with phase diagrams, X-ray diffraction of both annealed and quenched samples confirms the proposed structural transformations involving D03, L12 and D019 phases.