Flux Growth of Cerium Nickel Gallides Studied by In Situ Neutron Diffraction

Reactions of cerium and nickel in excess molten gallium were monitored by neutron diffraction during heating and cooling. The formation of binary intermediates CeGa₂ and Ni₂Ga₃ was observed during heating. During cooling of the molten mixture from 900 °C, precipitation of BaAl₄-type CeNi_0.74Ga_3.26 occurred at 850 °C. Upon cooling to 650 °C, this compound reacted in the flux to form Ce₂NiGa₁₀ and then Ce₂NiGa₁₂, the latter of which persisted to room temperature. Making use of this information, subsequent reactions were quenched at 750 °C to isolate crystals of CeNi_0.74Ga_3.26 for further study. Similar reactions replacing Ce with La and quenching above 750 °C yielded LaNi_0.35Ga_3.65 crystals. Magnetic susceptibility studies on CeNi_0.74Ga_3.26 indicate that the cerium is trivalent; the Ce³⁺ moments undergo a strongly anisotropic ferromagnetic ordering with moment perpendicular to the c axis below 7 K. Heat capacity data show little evidence of heavy fermion behavior. Resistivity measurements show that both LaNi_0.35Ga_3.65 and CeNi_0.74Ga_3.26 exhibit metallic behavior. Density of states calculations support this and indicate that Ni/Ga mixing in the compound stabilizes the structure.