Band structure calculations for Heusler phase Co 2YBi and half-Heusler phase CoYBi (Y=Mn, Cr)

Abstract

We have studied the electron structure and magnetic properties of Heusler phase Co 2YBi and half-Heusler phase CoYBi (Y=Mn, Cr) by using the full-potential linearized-augmented plane-wave (FLAPW) method. Co 2MnBi and Co 2CrBi are predicted to be half-metallic magnetism with a total magnetic moment of 6 and 5 μ B, respectively, well consistent with the Slater–Pauling rule. We also predict CoMnBi to be half-metallic magnetism with a slight compression. The gap origin for Co 2MnBi and Co 2CrBi is due to the 3d electron splitting of Mn (Cr) and Co atoms, and the gap width depends on Co electron splitting. The atom coordination surroundings have a great influence on the electron structure, and consequently the Y site in the X 2YZ structure has a more remarkable electron splitting than the X site due to the more symmetric surroundings. The investigation regarding the lattice constant dependence of magnetic moment shows that the Co magnetic moment exhibits an opposite behavior with the change of the lattice constant for Heusler and half-Heusler alloys, consequently leading to the different variation trends for total magnetic moment. The variation of total and atom magnetic moment versus lattice constant can be explained by the extent of 3d electron splitting and localization of Mn (Cr) and Co atoms for both the series of alloys.