FIRST PRINCIPLES STUDY OF ELECTRONIC STRUCTURE AND MAGNETIC PROPERTIES OF HALF-METALLIC FULL-HEUSLER ALLOYS Co₂MnSi and Co₂FeSi

We present a comprehensive investigation of the equilibrium structural, electronic and magnetic properties of Co₂MnSi and Co₂FeSi by density-functional theory (DFT) within the generalized gradient approximation (GGA) using the projected augmented wave (PAW) method. The on-site Coulomb interaction has also taken into account (GGA+U) approach to unravel the correlation effects on the electronic structure. The change of the energy gap, "spin gap", Fermi energy level and magnetic moments with the lattice parameters is investigated. We found that the on-site correlation interaction in Co₂FeSi is stronger than in Co₂MnSi. So on-site electronic correlation is necessary for Co₂FeSi and the magnetic moments reproduce experimental results well by GGA+U. Further we also found that a moderate change of the lattice parameters does not change the half-metallic ferromagnet (HMF) behavior for both materials. Appearance of half-metallicity is consistent with the integral magnetic moments, which also agrees with the experiment measurements.