FeGe (0 ≤ x ≤ 1) alloy series with plausible half-metallic behavior*

We report the synthesis and characterization of a Co_2-xTi_xFeGe (0 ≤ x ≤ 1) alloy series by substituting Co with Ti atoms in a stoichiometric Co₂FeGe alloy. Based on prior microscopic and structural characterization, Co₂FeGe is reported not to be phase pure¹. By Ti substitution, however, we investigated and found single-phase behavior for 0.375 ≤ x ≤ 0.875, while the other composition studied showed multi-phase behavior, supporting previous work. XRD analysis reveals cubic crystal structure for all single-phase samples with the lattice parameter increasing almost linearly with increasing Ti substitution. The extracted magnetic moments at 5 K show strong agreement with the Slater-Pauling moments.
Further, the spin-resolved DOS calculated predicts a gap in the minority channel. Moreover, with the addition of Ti, it is seen that the Fermi level shifts from the right edge of the band gap to the left and it falls exactly in the gap for x = 0.5.
Our experimental and theoretical studies of different single-phase sample compositions suggest that Co_1.5Ti_0.5FeGe is a plausible half metal.
References:
1. K.R. Kumar et al., IEEE Trans. on Magnetics 45, 10 (2009)