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

Abstract Twenty five new ternary Laves phases RET 4Mg and RET 4Cd (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 Ce1.41(1)Co4Mg0.59(1), Dy1.10(1)Co4Mg0.90(1), LaPt4Cd, Y1.10(1)Cu4Cd0.90(1), Ca0.93(1)Cd0.07(1)Pd2 and Eu0.87(2)Cd0.13(2)Pd2 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 MgCu2 structure, while the annealed ones adopt the MgCu4Sn 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 REPt4Cd (RE = La–Nd) samples have been characterized with respect to their magnetic properties. LaPt4Cd is a diamagnet, while CePt4Cd (2.23(1) µB), PrPt4Cd (3.40(1) µB) and NdPt4Cd (3.43(1) µB) are Curie–Weiss paramagnets. The cerium compound shows a slight moment reduction. NdPt4Cd is ordered ferromagnetically at T C = 4.4(1) K.