Microstructure and magnetostrictive behavior of Fe-15 at% Ga alloy with different cooling rates

The main attention of this paper was devoted to the study of the effect of different cooling rates on the magnetic domain configuration and magnetostrictive behavior of heat-treated Fe-15 at% Ga alloy. After annealing at 1,000 A degrees C for 3 h, the samples were subjected to water quenching, air cooling, and furnace cooling treatments. Phase constitution and magnetic domain structures of the samples were studied using X-ray diffraction (XRD) and magnetic force microscopy (MFM). XRD results indicate a single phase of alpha-Fe with disordered bcc (A2) structure for all samples. MFM results show that both water-quenched (WQ) and air-cooled (AC) samples are mainly made from ordered stripe domain structures, whereas a mixture of irregular stripe, zigzag, and plate domain patterns are observed in furnace-cooled (FC) sample. Magnetostrictive strain was measured in the presence of an externally applied magnetic field. It is found that WQ sample has the highest magnetostriction, while AC and FC samples exhibit moderate and the lowest magnetostriction, respectively, against the applied field. The dependence of initial domain configurations on thermal history is found to be conducive to the change in saturation magnetostrictions of the samples.