We investigate the atomic disorder effects on the half-metallicity of the full-Heusler alloy ${\mathrm{Co}}_2\left({\mathrm{Cr}}_{1-x}{\mathrm{Fe}}_x\right)\mathrm{Al}$ from first principles by using the Korringa-Kohn-Rostoker method with the coherent potential approximation. Our results show that disorder between Cr and Al does not significantly reduce the spin polarization of the parent alloy ${\mathrm{Co}}_2\mathrm{CrAl},$ while disorder between Co and Cr makes a considerable reduction of the spin polarization. It is observed that the spin polarization of ${\mathrm{Co}}_2\left({\mathrm{Cr}}_{1-x}{\mathrm{Fe}}_x\right)\mathrm{Al}$ decreases with increasing Fe concentration x in both the ordered ${L2\mathrm{}}_1$ and the disordered $B2\mathrm{}$ structures, and that the effects of the disorder on the spin polarization is significant at low Fe concentrations. The results suggest that a highly spin-polarized ferromagnet with high Curie temperature will be obtained if a ${\mathrm{Co}}_2\left({\mathrm{Cr}}_{1-x}{\mathrm{Fe}}_x\right)\mathrm{Al}$ with the ordered ${L2\mathrm{}}_1$ structure can be fabricated at low Fe concentrations.

• Received 20 September 2003

DOI:https://doi.org/10.1103/PhysRevB.69.144413