Schematic illustration of the (a) L21 and (b) Hg2CuTi structures and their calculated magnetic structures. The nearest (N)—neighbour relation between the AC and BD layers and the next-nearest (NN)—neighbour relation within these layers is indicated.
Dependence of the lattice constant on the annealing temperature for ball-milled Fe2CrGa samples (A-samples). The inset shows the XRD patterns.
Dependence of the Curie temperature on the annealing temperature for (a) A- and (b) B-samples. The insets show the M vs T curves.
SAED patterns of (a) the A-sample annealed at 1073 K and (b) the B-sample annealed at 573 K with the electron beam parallel to the  and  directions, respectively.
Saturation magnetization M S of A- and B-samples as a function of annealing temperature. The inset shows the M vs H curves at 5 K for the as-milled and the 1073/1473 K annealed B-samples. For comparison, the saturation moment of the arc-melted (not ball-milled) samples is also presented.
Total energies and magnetic moments (stars) calculated by CPA as a function of degree of disorder in Fe2CrGa, (a) considering and (b) not considering magnetic interactions. The upper dashed areas represent the range of measured magnetic moments in the present work and the lower one is the range of moments reported in previous work. 15,16 The energy increment of the vertical axis is 0.02 Ry/atom ≈ 0.272 eV/atom ≈ 26.2 kJ/mol of atoms.
Atomic configurations and magnetic structures of (a) Hg2CuTi with (b) AD disorder, and (c) CD disorder.
Atomic moments calculated upon increasing atomic disorder from the Hg2CuTi to the A2 structure. The dashed area represents the range of measured magnetic moments in the present work.
Total energies and magnetic moments calculated by CPA for some particular atomic configurations: L21, Hg2CuTi, A2 (100% disorder at four sites) and B2 (100% disorder at two sites). B21 BD stands for Cr/Ga disorder at B/D sites in the L21 structure, while B22 BD represents the Fe/Ga disorder at B/D sites in the Hg2CuTi structure. Due to the equivalence of the other B2-type states in L21 and Hg2CuTi, the states of B2AD, B2AC, B2CD, and B2BC are all based on the disorder of Hg2CuTi.
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