Order–disorder transition of vacancies from the full- to the half-Heusler structure in Ni2−xMnSb alloys

The thermal transformations and crystal structures in the ordered bcc phases appearing in Ni 2− x MnSb alloys have been investigated. Thermo-analyses on NiMnSb( x = 1) show three λ-shaped peaks suggesting a magnetic and chemical ordering transitions at approximately 450, 865 and 965 °C. With decreasing x , the first and second peak temperatures gradually decrease, while the third one increases. By Z- contrast imaging technique, it was confirmed that the second peak corresponds to the order-disorder transition of vacancies from the L 2 1 to the C 1 b structure.