Effect of interstitial additions on magnetostriction in Fe–Ga alloys

Abstract

The additions of trace amounts of small interstitial atoms (carbon, boron, and nitrogen) to Fe–Ga (Galfenol) alloys have a small but beneficial effect on the magnetostriction of Fe–Ga alloys especially at high Ga compositions. The saturated magnetostrictions [(3∕2)λ100’s] of both slow cooled and quenched single crystal Fe–Ga–C alloys with Ga contents >18at.% are about 10%–30% higher than those of the comparable binary Fe–Ga alloys. For boron and nitrogen additions, the magnetostrictions of slow cooled alloys with Ga content >18at.% were approximately 20% higher than those of the binary Fe–Ga alloys. We assume that these small atoms enter interstitially into the octahedral site as in pure α-Fe and inhibit chemical ordering, resulting in increased λ100. Thermal analysis of the Fe–Ga binary alloys and Fe–Ga–C ternary alloys indicates that the addition of C into the Fe–Ga system decreases the formation kinetics of D03 and extends the disordered region beyond the maximum for slow cooled binary samples.