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Zusammenfassung:
Ternary gallides with the chemical formula RECuxGa4 − x have been synthesized from the elements by arc melting. Characterization by X-ray powder diffraction analysis confirmed isotypism with the crystal structure of BaAl4 for all the early rare earth members RE ; La, Ce, Pr, Nd, Sm and Gd.
In case of the solid solution CeCuxGa4 − x, the homogeneous region at 600°C has been determined ranging from x = 0.4 to x = 1.7. Similar to CeNixGa4 − x, the dependence of the volume and of the c parameter as a function of the copper concentration exhibits a large positive deviation from Vegard's rule.
Magnetic behaviour was studied in the temperature range 4.5–900 K. LaCuGa3 is weakly temperature dependent. Above LNT the magnetic susceptibilities of the cerium, praseodymium and neodymium and gadolinium compounds essentially correspond to a paramagnetism of the tripositive rare earth elements. SmCuGa3 reveals a typical Van-Vleck paramagnetism of closely spaced multiplets (μeff = 1.58 μB at 300 K). Magnetic ordering generally occurs below 10 K in the form of antiferromagnetic coupling for the samarium and gadolinium compounds whereas ferromagnetism is observed for the cerium, praseodymium and neodymium alloys.
