Ternary Laves phases with the MgCu4Sn-type structure: RECo4Mg (RE = Gd, Dy–Tm, Lu), EuNi4Mg and RET 4Cd (RE = Y, La–Nd, Sm, Gd–Dy; T = Cu, Pt)

Abstract Twenty five new ternary Laves phases RET 4 Mg and RET 4 Cd ( RE = rare earth element; T = Co, Ni, Cu, Pt) have been synthesized from the elements using niobium or tantalum tubes as inert crucible materials. The lattice parameters have been derived from powder X-ray diffraction data. The structures of Ce 1.41(1) Co 4 Mg 0.59(1) , Dy 1.10(1) Co 4 Mg 0.90(1) , LaPt 4 Cd, Y 1.10(1) Cu 4 Cd 0.90(1) , Ca 0.93(1) Cd 0.07(1) Pd 2 and Eu 0.87(2) Cd 0.13(2) Pd 2 were refined from single-crystal X-ray diffractometer data. Most phases show certain degrees of RE /Mg or RE /Cd disorder. The quenched phases are assigned to the MgCu 2 structure, while the annealed ones adopt the MgCu 4 Sn type, a translationengleiche superstructure variant of the aristotype. The annealing time has a substantial influence on the degree of ordering and is expressed in the lattice parameters, i.e. larger ones for the disordered samples. The RE Pt 4 Cd ( RE = La–Nd) samples have been characterized with respect to their magnetic properties. LaPt 4 Cd is a diamagnet, while CePt 4 Cd (2.23(1) µ B ), PrPt 4 Cd (3.40(1) µ B ) and NdPt 4 Cd (3.43(1) µ B ) are Curie–Weiss paramagnets. The cerium compound shows a slight moment reduction. NdPt 4 Cd is ordered ferromagnetically at T C = 4.4(1) K.