Theoretical study of the electronic and magnetic structures of the Heusler alloys Co2Cr1-xFexAl -: art. no. 054441

The electronic structure, x-ray absorption (XAS), x-ray magnetic circular dichroism (XMCD), and magneto-optical spectra of the doped Heusler alloys Co2Cr1-xFexAl (x=0, 0.125, 0.25, 0.375, 0.5, 0.625, 0.75, and 1) were investigated theoretically from first principles, using the fully relativistic Dirac linear-muffin-tin-orbital band structure method. It was shown that the concentration and arrangement of Fe atoms in the lattice play the leading role in the formation of the magnetic properties of the compounds, determining to a considerable extent the magnetic states of Co and Cr atoms. The spin polarization of electron states at the Fermi energy is quite high (about 95%) for the compositions between x=0 and x=0.4, owing to the presence of high peaks of majority-spin Cr and Co d density of states at the Fermi energy. Further increasing of Fe content leads to the abrupt decreasing of the spin polarization of carriers. The band structure calculations in the LSDA approximation reproduce quite well the shape of the XAS and XMCD spectra at the Co, Fe, and Cr L-2,L-3 edges. The energy dependence of the matrix elements affects strongly the values of both the spin and the orbital magnetic moments derived from the calculated XAS and XMCD spectra using the sum rules. Our calculations show that the magneto-optical measurements are sensitive to changes in the structure of compounds (doping, disorder, etc.) accompanied by changes of the magnetic states of atoms.