Slater-Pauling behavior and origin of the half-metallicity of the full-Heusler alloys

TLDR

The study explains why the spin‑down band contains exactly 12 electrons, demonstrates that the rule M_t = Z_t − 24 holds for compounds with fewer than 24 valence electrons, and discusses deviations and differences from half‑Heusler alloys. The authors employ the full‑potential screened Korringa‑Kohn‑Rostoker method to investigate full‑Heusler alloys based on Co, Fe, Rh, and Ru, and use group‑theoretical arguments to analyze the spin‑down band occupancy and rule deviations. Many of the examined full‑Heusler compounds exhibit half‑metallicity with an extremely small minority‑band gap, and they follow a Slater‑Pauling rule where the total spin‑magnetic moment per unit cell equals the total valence electrons minus 24.

Abstract

Using the full-potential screened Korringa-Kohn-Rostoker method we study the full-Heusler alloys based on Co, Fe, Rh and Ru. We show that many of these compounds show a half-metallic behavior, however in contrast to the half-Heusler alloys the energy gap in the minority band is extremely small. These full-Heusler compounds show a Slater-Pauling behavior and the total spin-magnetic moment per unit cell (M_t) scales with the total number of valence electrons (Z_t) following the rule: M_t=Z_t-24. We explain why the spin-down band contains exactly 12 electrons using arguments based on the group theory and show that this rule holds also for compounds with less than 24 valence electrons. Finally we discuss the deviations from this rule and the differences compared to the half-Heusler alloys.