New Manganese-Bearing Antimonides and Bismuthides with Complex Structures. Synthesis, Structural Characterization, and Electronic Properties of Yb₉Mn_4+xPn₉ (Pn = Sb or Bi)

Reported are structure and property studies on a series of isostructural compounds with general formulas Yb 9 Mn 4+ x Sb 9 ( x ≈ 0.2), A 9 Mn 4+ x Bi 9 ( A = Ca and Yb; x ≈ 0), and the Zn-substituted derivatives Yb 9 (Mn,Zn) 4+ x Sb 9 (0 < x < 0.4). They have been synthesized from the corresponding elements by high-temperature reactions, and their structures have been established by single-crystal X-ray diffraction. Despite being nearly stoichiometric phases, whose average crystallographic arrangement can be described with the orthorhombic Ca 9 Mn 4 Bi 9 type structure (space group Pbam, No. 55), these ternary materials exist within narrow homogeneity ranges, whereupon an interstitial site is partially occupied by the transition metal. Electronic structure calculations confirm that the “empty” A 9 Mn 4 Sb 9 or A 9 Mn 4 Bi 9 structures are electron deficient, making them suitable hosts for small dopant atoms. The expected poorly metallic behavior is evidenced from temperature-dependent resistivity data gathered from single-crystals. Magnetic susceptibility measurements in the range 2−350 K reveal complex antiferromagnetically coupled structures. These experimental results are further corroborated by theoretical calculations based on the linear muffin-tin orbital (LMTO) and the full potential linearized augmented plane wave (FP-LAPW) methods.