The quaternary intermetallics Ce2CoGa9Ge2, Ce2NiGa9Ge2, and Sm2NiGa 9Ge2 were prepared by reacting elemental metals in excess of gallium at 850°C. The title compounds crystallize in the tetragonal space group P4/nmm in the Sm2Ni(Si1-xNix)Al 4Si6 structure type with cell parameters a = 5.9582(5) Å, c = 15.0137(18) Å, and a = 5.9082(17) Å, c = 14.919(6) Å, Z = 2, for Ce2CoGa9Ge2 and Sm 2NiGa9Ge2, respectively. The structures are composed of covalently bonded three-dimensional networks of [CoGa 9Ge2] in which the rare-earth metals fill the voids forming a 2D square net. The structures of RE2MGa9Ge 2 are Ga-rich and possess extensive Ga-Ga bonding even though the Ga atoms do not form a network on their own. Magnetic susceptibility measurements for Ce2CoGa9Ge2 and Ce2NiGa 9Ge2 show Curie-Weiss paramagnetism, consistent with presence of Ce3+ ions. Magnetocrystalline anisotropy was observed for Ce2NiGa9Ge2, with the magnetically easy axis lying along the  crystallographic direction. A transition to an antiferromagnetic state was observed below 4 K in the easy direction of magnetization. In the magnetically hard direction of the basal plane, paramagnetic behavior was observed down to 1.8 K.
ASJC Scopus subject areas
- Physical and Theoretical Chemistry
- Inorganic Chemistry