STRUCTURE AND PROPERTIES OF THE TRANSITION-METAL ZINTL COMPOUNDS - A14MNBI11 (A = CA, SR, BA)

A14MnBi11 (A = Ca, Sr, Ba) is synthesized by reacting the elements in stoichiometric amounts at high temperatures (950-1350-degrees-C). Single-crystal X-ray diffraction data (130 K, a = 17.002 (6) angstrom, c = 22.422 (7) angstrom (Ca); a = 17.820 (6) angstrom, c = 23.394 (6) angstrom (Sr); a = 18.633 (8) angstrom, c = 24.340 (10) angstrom (Ba)) were refined (tetragonal, I4(1)/acd(142), Z = 8, R = 5.4%, R(w) = 5.9% (Ca), R = 4.1%, R(w) 4.7% (Sr), R = 5.1%, R(w) = 4.9% (Ba)) and showed these compounds to be isostructural to the main-group analogues, Ca14AlSb11 and A14GaAs11 (A = Ca, Sr). Magnetization measurements performed on powder samples have shown that Ca14MnBi11 and Sr14MnBi11 are ferromagnets and that Ba14MnBi11 is an antiferromagnet. The magnetic coupling between Mn ions is attributed to an RKKY interaction, and thus metallic behavior is expected. The temperature dependence of the resistivity of pressed pellets is presented and suggests that all three compounds are metals.