Electronic and magnetic properties of Fe_3−x Cr _x Si ordered alloys from first principles

Density functional theory calculations are performed to investigate the electronic and magnetic properties of Fe_3−x Cr _x Si alloys with Cr concentration in the range of 0.25 ≤ x ≤ 2.75. The L2₁ phase is found to be a more stable one in comparison with the A15 phase for x ≤ 1.50 beyond which the A15 phase becomes more stable. Alloys with the stable L2₁ phase are found to be metallic for x ≤ 0.75, however, a half metallic behavior is found at x = 1.00, 1.25, and 1.50 with band gaps of 0.60, 0.24, and 0.21 eV, respectively. In contrast, all A15 structures are found to be metallic. The total magnetic moments are found to decrease for L2₁ phase from 14.4 μ_B/cell at x = 0.25 to zero at x = 2.00 with non-integer values for the metallic structures and integer values for the half-metallic. However, a monotonic decrease is found for the case of A15 phase with values larger than those of L2₁ phase.