Electronic structure and magnetism of Fe3-xVxX (X=Si, Ga, and Al) alloys by the KKR-CPA method

We present first-principles charge- and spin-self-consistent electronic str ucture computations on the Heusler-type disordered alloys Fe3-xVxX for thre e different metalloids X = (Si, Ga, and Al). In these calculations we use t he methodology based on the Korringa-Kohn-Rostoker formalism and the cohere nt-potential approximation generalized to treat disorder in multicomponent complex alloys. Exchange correlation effects are incorporated within the lo cal spin density approximation. Total energy calculations for Fe3-xVxSi sho w that V substitutes preferentially on the Fe(B) site, not on the Fe(A,C) s ite, in agreement with experiment. Furthermore, calculations have been carr ied out for Fe3-xVxX alloys (with x = 0.25, 0.50, and 0.75), together with the end compounds Fe3X and Fe2VX, and the limiting cases of a single V impu rity in Fe3X and a single Fe(B) impurity in Fe2VX. We delineate clearly how the electronic states and magnetic moments at various sites in Fe3-xVxX ev olve as a function of the V content and the metalloid valence. Notably, the spectrum of Fe3-xVxX (X = Al and Ga) develops a pseudogap for the majority as well as minority spin states around the Fermi energy in the V-rich regi me, which, together with local moments of Fe(B) impurities, may play a role in the anomalous behavior of the transport properties. The total magnetic moment in Fe3-xVxSi is found to decrease nonlinearly and the Fe(B) moment t o increase with increasing x; this is in contrast to expectations of the "l ocal environment" model, which holds that the total moment should vary line arly while the Fe(B) moment should remain constant. The common-band model, which describes the formation of bonding and antibonding states with differ ent weights on the different atoms, however, provides insight into the elec tronic structure of this class of compounds. [S0163-1829(99)11543-1].