Experimental and theoretical study of the electronic structure of Fe, Co, and Ni aluminides with theB2 structure

The differences in electronic structure of B2-type (CsCl) transition-metal aluminides (FeAl, CoAl, and NiAl) have been investigated by comparing data obtained using electron energy-loss spectroscopy with theoretical calculations of the spectra. The densities of states (DOS) for the three alloys calculated using the ab initio self-consistent linear muffin-tin orbital method within the local density approximation have been compared. Using the unoccupied part of the DOS and the relevant transition matrix elements, energy-loss spectra have been calculated. It is noted that a rigid band model can only be considered as a first approximation to calculate the trends in the electronic structure of the alloys. The Al L_2-3 and K edges (providing information on s+d and p symmetry of final states at the Al sites, respectively) and the transition-metal L_2-3 edges (s+d symmetry of final states at the transition-metal sites) have been studied. Good agreement has been found between experiment and calculations and, from the interpretation of spectral details in terms of site and angular momentum decomposed density of states, hybridization and interaction between the Al sp and TM d bands is observed and thus a covalent character in the bond is concluded. The differences in the electronic structure of the alloys studied, both in terms of band filling and density of states at the Fermi level, have been correlated with the variation of the macroscopic properties of the materials. {} 1996 The American Physical Society.