In situ neutron diffraction study of bulk phase transitions in Fe-27Ga alloys

Highly thermal-stable ferromagnetism by a natural composite

“…1a clearly show that the first magnetization drop at ∼700 K corresponds to the Curie transition of DO 3 phase27, where the net magnetization reduces by over 80 % when compared with that at 300 K, indicating that the DO 3 phase has a relatively large volume fraction. The following changes are consistent with the equilibrium phase diagram19, which are the bcc→L1 2 and ferromagnetic L1 2 →paramagnetic DO 19 transformations, respectively272833. Evidence for the bcc→L1 2 transformation is presented by the blue curve in the X-ray diffraction data in Fig.…”

“…In fact, this transformation follows well the Fe–Ga equilibrium phase diagram19. Such transformation has also been verified by an in situ heating neutron diffraction study33 and a quasi in situ X-ray diffraction study27. As reported in a similar alloy Fe 3 Ge (ref.…”

“…35), the numerous stacking fault debris and twining boundaries existed in the L1 2 phase act as efficient nucleation site for DO 19 phase by a shear-type mechanism. Consequently, the L1 2 →DO 19 transformation is very fast, which is observed to be of the order of 300 s. The in situ neutron diffraction study by Golovin et al 33. shows that the L1 2 →DO 19 transformation in the Fe 73 Ga 27 alloy between two closed packed lattices takes place in very small temperature intervals (Δ T ≈10 K), demonstrating its fast transformation kinetics, and they also observed a similar sudden decrease of magnetization.…”

Anelasticity of Phase Transitions and Magnetostriction in Fe-(27-28%)Ga Alloys

“…Here, we can only specify that it is the D0 19 → B2 → A2 transition. According to the in situ neutron diffraction study, if the heating rate is 2 K/ min, there is not enough time for the B2 → A2 reaction, whereas in the case of heating with a rate of 1 K/min, the neutron diffraction detects weak B2 ordering of the A2 phase, as discussed in 6 . The Tr3 peak splitting with an increase in the heating rate (Fig.…”

“…This effect relates to a complex phase transformation sequences in the Fe-27%Ga alloys. Phase transitions in Fe 3 Ga-type alloys were first studied by X-ray diffraction [3][4][5] , and more recently by in situ neutron diffraction 2,6,7 to characterize the bulk alloy. Different ratios between metastable and equilibrium phases characterized by magnetostriction values of different signs vary the magnetostriction values of the alloy, λ S , from positive to negative, including the value of λ S = 0 2 .…”