Electronic and Magnetic Properties of X₂Mn_1-xV_xSi (X=Fe and Co)

Abstract

We have performed energy-band calculations of X₂Mn_1-xV_xSi (X=Fe and Co) at x=0, 0.25, 0.5, 0.75, 1.0. In ferromagnetic ordering, we obtain excellent agreement between calculated and experimental data for the magnetic moment per formula unit and the lattice constant, at each Mn content. We have obtained the result that state densities in Fe₂Mn_1-xV_xSi have a large peak at the Fermi level, while they do not in Co₂Mn_1-xV_xSi. We have also estimated Heisenberg exchange constants from total energy differences between ferromagnetic and antiferromagnetic orderings. The Curie temperature roughly calculated from the exchange constants increases from x=0 to x=0.5 and then decreases rapidly in Fe₂Mn_1-xV_xSi, though it monotonically decreases from x=0 to x=0.75 in Co₂Mn_1-xV_xSi. The behavior of calculated Curie temperatures in Fe₂Mn_1-xV_xSi is consistent with the observed one.