Experimental and theoretical investigation of the chromium–vanadium–antimony system

Abstract

Abstract The binary compound V3Sb (V2.64Sb, V3Sb and V3.24Sb) was synthesized as thin multilayered films with varying V:Sb ratios. The V-content determines the crystallization temperature and it is highest for the film with the lowest amount of V. Ternary chromium–vanadium–antimony (Cr–V–Sb) films were prepared containing Cr from 10 to 51 at-% with the Sb content fixed to yield M3Sb (M=Cr, V). In the as-deposited state the layers are already interdiffused which is most likely caused by the very low repeating unit thickness between 0.29 and 0.68 nm investigated by X-ray diffraction experiments. All ternary compounds crystallized from the amorphous state with crystallization temperatures depending more on the repeating unit thickness than on chemical composition. For most samples the simultaneous crystallization of the two phases M3Sb (A15 structure type) and MSb is observed. The crystalline A15 compounds are only stable in a limited temperature range and decompose at elevated temperatures. Compared to the binary Cr–Sb system crystallization of the hexagonal phase MSb (M=Cr, V) occurs at remarkably higher temperatures, i.e. in the ternary system nucleation and crystallization of this phase is hindered. The chemical composition requires short-range composition fluctuations to nucleate the binary phase. The first principles total energy calculations using the spin-polarized relativistic Korringa–Kohn–Rostoker (SPR-KKR) method confirm the experimental observations concerning the concentration-dependent stability of different phases of the Cr–V–Sb system. For the ratio M:Sb=3:1 the system is preferably stabilized in the A15 crystal structure for all possible Cr and V concentrations, while an increase of Sb content up to M:Sb=2:1 results in the stabilization of the Ni2In structure for almost all Cr concentrations. Only in the V-rich regime of the system the Heusler Ni2MnAl-type structure was found to be energetically more preferable.