Effect of low-valent atom substitution on electronic structure and magnetic properties of Fe1.5M0.5CoSi (M=V, Cr, Mn, Fe) Heusler alloys

Quaternary Heusler alloys Fe1.5M0.5CoSi with M=V, Cr, Mn and Fe have been investigated theoretically and experimentally. All of these samples crystallize in the ordered Heusler-type structure. The calculated electronic structure shows a pseudogap around EF in the minority spin states of Fe2CoSi. With the substitution of low-valent atoms for Fe, the majority antibonding peak is shifted to higher energy and a minority gap around the Fermi level is opened. High spin polarization ratio is obtained in Fe1.5M0.5CoSi (M=V, Cr, Mn) alloys. The calculated total spin moments decrease with decreasing number of valence electrons and follow the Slater–Pauling curve, which agree with the experimental results well. The Curie temperature decreases as M atom varies from Fe to V, but is always higher than 650 K, which is suitable for technical applications.

► New half-metallic materials in Fe-based Heusler alloys Fe1.5M0.5CoSi with M=V, Cr, Mn. ► Half-metallic ferromagnets with high Curie temperatures and tunable magnetic moments. ► Effect of low-valent transition metal elements on the electronic structure and formation of half-metallicity in doped Fe2CoSi has been studied.