Off‐Stoichiometry Quaternary Heusler‐Like Semiconductors with Magnetism and Disorder

Abstract

AbstractThe theoretical finding of a large group of intrinsic off‐stoichiometry quaternary Heusler‐like semiconductors with mixing and tunable occupation of 4c‐4d atomic sites, such as FexCoyTiSb with non‐integer x + y > 1 are reported. Those semiconductors are never reported before, and they radically break the well‐recognized 18‐ (or 24‐) valence electron counting (VEC) rule and the exact 4c‐ (or both 4c‐ and 4d‐) atomic sites stoichiometry for the traditional quaternary half‐Heusler (or full‐Heusler) semiconductors. Physically, the novel semiconductors can be designed by following a d‐orbital‐determined compensation rule. The extra atoms fill in the tetrahedral vacancies of the half‐Heusler structure, introduce symmetry‐constrained d orbitals near the Fermi level, large crystal field splitting, and then form a bandgap at appropriate fractional compositions, which leads to an exact compensated electronic structure. The newly established compensation rule reveals an abundant phase space of the quaternary Heusler‐like (2x + 3y = 3 for VECY+Z = 9, 2x + 3y = 4 for VECY+Z = 8, and 2x + 3y = 5 for VECY+Z = 7) compounds. High‐throughput screenings reveal many new FexCoyYZ semiconductors, all of which possess strong disorder, weak magnetism, spin compensation, and wide composition‐range tunability. The intertwined orders may either find functionalities surpassing the existing materials or give rise to new potential applications.