Temperature-Induced Phase Transitions of Fe-Ga Alloys for Sensors

Abstract

Slow cooled arc melted Fe-Ga alloys with different compositions were characterized. GI-XRD confirms the BCC structure and existence of single phase A2 in 17 at.% of Ga and multiphase A2 and L12 in 30 at. % of Ga. The Ga defects migrates during annealing and reduces the lattice. The Galfenol alloy with the 30 at.% of Ga has an A2 phase around 400 oC and an L12 phase around 560 oC. The formation of the L12 structure is due to an exposure in high temperature region. The magnetostriction of Fe83 - Ga17 and Fe70 - Ga30 alloys seems to be 64 and 27 ppm. Decrement of magnetostriction is due to change in anisotropy coefficient.