Temperature-Dependent Products in Gallium Flux Reactions of Cerium and Transition Metals

Reactions of cerium and transition metals in excess molten gallium were carried out, exploring the formation of different cerium intermetallics as the flux reaction is cooled. Ce/T/Ga reactions with T = Ni, Cu, Pd, Ag, and Zn produce a high-temperature product, which converts into a low-temperature product in the flux. The phases present in the flux mixture were determined by quenching identical reactions at 750 and 300 °C and identifying the isolated products using elemental analysis and X-ray diffraction. The compounds CeGa₂, CeCu_0.37Ga_3.63, CePd_0.32Ga_3.68, Ce₅Ag_1.76Ga_17.29, and Ce₅Zn_1.37Ga_17.73 were isolated by quenching at 750 °C. Upon cooling to 300 °C, the corresponding reactions instead yielded CeGa₆, Ce₂CuGa₁₂, Ce₂PdGa₁₂, Ce₂Ag_0.7Ga_9.1, and CeZnGa_7-. All of these structures contain cerium in the ThCr₂Si₂-related layers. Large crystals of high-temperature products CeCu_0.37Ga_3.63, CePd_0.32Ga_3.68, Ce₅Ag_1.76Ga_17.29, and Ce₅Zn_1.37Ga_17.73 were used for magnetic susceptibility measurements. All of these materials show highly anisotropic ferromagnetic ordering of Ce³⁺ moments below 8 K, which is in contrast to the antiferromagnetism seen for the compounds that were isolated at 300 °C.