Roles of solidification rate and Co substitution for Cr on single phase ordered Fe2CrSi alloy formation

Abstract

A comprehensive experimental and theoretical study on the structural, electronic, and magnetic properties of bulk Co-substituted Fe2CrSi Heusler alloys has been carried out. The impact of rapid solidification on the formation of phase pure Fe2CrSi alloy has also been explored. Bulk Fe2Cr1-xCoxSi (where x = 0, 0.1, 0.2, 0.3, and 0.5) alloy samples were prepared using arc melting, and melt-spinning was employed to prepare Fe2CrSi ribbons at two different wheel velocities (20 and 30 ms−1). Our investigation revealed that the Fe2CrSi Heusler alloys with a Co substitution in the range of 0.2 ≤ x ≤ 0.5 exhibited a single L21 phase structure. However, for x = 0 and 0.1, there were 27 % and 11 % A15 impurity phases, respectively, coexisting with the L21 phase. On the other hand, the sample melt-spun at 20 ms−1 contained only 7 % impurity phase, while the one melt-spun at 30 ms−1 was free of any impurity phase. First principles calculations using the GGA + U approach showed that the single phase ribbon sample exhibited 12.5 % DO3 type disorder, indicating a change in site preference resulting from a high solidification rate. All the experimental and calculated magnetic moments of the alloys were in agreement with the Slater-Pauling rule. Our results suggest that the Fe2Cr0.75Co0.25Si alloy is a promising candidate for spintronic device applications due to its half-metallic nature.