Iron-gallium alloys : temperature and field effects on [lambda]100 and magnetic anisotropy measurements

Abstract

Magnetostriction measurements were taken on samples of Fe-Ga alloys (Galfenol) containing between 18% and 35% Ga in fields of 5 kOe to 24 kOe from room temperature to liquid nitrogen temperature. In addition, room temperature magnetic anisotropy measurements were conducted on samples between 8% Ga and 25% Ga. No major hysteresis was found in any of the samples and the field dependence was found to be modest (-2%). Anomalous temperature dependence was found in 22-24% Galfenol, where magnetostriction decreased with decreasing temperature, and 35% Galfenol, where magnetostriction increased dramatically (over 50% to values up to about 250 parts per million) with decreasing temperature. Quenching to retain [alpha]-iron and B2 (CsCl) phases was found to increase magnetostriction, with the B2 structure creating the largest magnetostriction. The reasons for the atypical temperature dependence and the B2 structure enhancing magnetostriction are still unexplained. K anisotropy constants were found to decrease with increasing Ga concentration, but more samples need to be measured to validate this trend.