Thermally driven large magnetoresistance and magnetostriction in multifunctional magnetic FeGa–Tb alloys

The temperature stability of Fe81Ga19Tbx (x = 0.3) and Fe81Ga19 (i.e. Galfenol) alloys is investigated over a temperature range from 10 to 1000 K. High-temperature measurement of magnetization indicates that Tb-doped FeGa results in a Curie temperature rise of ∼150 K, while saturation magnetization and magnetostrictive coefficient increase by 7% and 2.5-fold, respectively, compared to the parent Fe81Ga19 alloy. It is noticed that Fe81Ga19Tbx (x = 0.3) alloy not only gives rise to a noticeable stabilization of magnetic moment below room temperature, but also presents a dramatic decrease in temperature coefficient of magnetostriction by ∼30%. Most interestingly, a large negative magnetoresistance (MR) of −25% at 10 kOe is observed at low temperature, ∼75 K for a magnetostrictive Fe81Ga19 alloy. Ferromagnetic and antiferromagnetic behaviors occur simultaneously in the temperature range conducive to a large MR. Furthermore, the large MR is also assumed to relate to a weak spin glass phase of the alloy observed at cryogenic temperatures and confirmed by ac susceptibility measurements.