Structure and Properties of Single Crystalline CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2

Single crystals of CaMg2Bi2, EuMg2Bi2, and YbMg2Bi2 were obtained from a Mg-Bi flux cooled to 650 degrees C. These materials crystallize in the CaAl2Si2 structure-type (P (3) over bar m1, No. 164), and crystal structures are reported from refinements of single crystal and powder X-ray diffraction data. EuMg2Bi2 displays an antiferromagnetic transition near 7 K, which is observed via electrical resistivity, magnetization, and specific heat capacity measurements. Magnetization measurements on YbMg2Bi2 reveal a weak diamagnetic moment consistent with divalent Yb. Despite charge-balanced empirical formulas, all three compounds are p-type conductors with Hall carrier concentrations of 2.0(3) x 10(19) cm(-3) for CaMg2Bi2, 1.7(1) x 10(19) cm(-3) for EuMg2Bi2, and 4.6(7) x 10(19) cm(-3) for YbMg2Bi2, which are independent of temperature to 5 K. The electrical resistivity decreases with decreasing temperature and the resistivity ratios rho(300 K)/rho(10 K) <= 1.6 in all cases, indicating significant defect scattering.