Doping and disorder in the Co2MnAl and Co2MnGa half-metallic Heusler alloys

We expand our study of the full-Heusler compounds [I. Galanakis , Appl. Phys. Lett. 89, 042502 (2006)] to cover also the case of doping and disorder in the case of Co2MnAl and Co2MnGa half-metallic Heusler alloys. These alloys present a region of very small minority density of states instead of a real gap. Electronic structure calculations reveal that doping with Fe and Cr in the case of Co2MnAl retains half-metallicity contrary to the Co2MnGa compound. Cr impurities present an unusual behavior, and the spin moment of the Cr impurity scales almost linearly with the concentration of Cr atoms contrary to Co(2)MnZ (Z=Si,Ge,Sn) where it was almost constant. Half-metallicity is no longer preserved for both Co2MnAl and Co2MnGa alloys when disorder occurs and there is an excess of either Mn or sp atoms.