Effect of interstitial additions on magnetostriction in Fe-Ga alloys

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)lambda(100)'s] of both slow cooled and quenched single crystal Fe-Ga-C alloys with Ga contents >18 at. % 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 >18 at. % 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 alpha-Fe and inhibit chemical ordering, resulting in increased lambda(100). 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 D0(3) and extends the disordered region beyond the maximum for slow cooled binary samples. (C) 2008 American Institute of Physics.