MAGNETIC-BEHAVIOR AND STRUCTURAL CHEMISTRY OF TERNARY GALLIDES LACUXGA4-X CECUXGA4-X, PRCUXGA4-X, NDCUXGA4-X, SMCUXGA4-X, GDCUXGA4-X

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. © 1990.