Structure and physical properties of quaternary Heusler alloy NiMnCuSb

The relationship between structure and physical properties such as magnetic moment and Curie temperature is studied theoretically for the recently synthesized equiatomic quaternary Heusler alloy CuNiMnSb, which is found to crystallize in the LiMgPdSb structure. Calculations are performed for various different possible structural phases within the framework of the D03-type structure (space group F4¯3m) by changing the sequence of the atoms along the body diagonal of fcc lattice that characterizes the structure of this alloy. Total energy, magnetic moment and the Curie temperature results, in particular the latter two, suggest that the correct order of the atoms along the body diagonal is most likely Ni(0,0,0), Mn(0.25,0.25,0.25), Cu(0.5,0.5,0.5) and Sb(0.75,0.75,0.75) in contrast to (disagreement with) the conclusions of a recent experimental study. Neither the sequence Ni-Cu-Mn-Sb nor Ni-Mn-Cu-Sb shows a large spin polarization at the Fermi level.