Ternary aurides RE ₄Mg₃Au₁₀ (RE = La, Ce, Pr) and RE ₄Cd₃Au₁₀ (RE = Y, La–Nd, Sm, Gd–Dy) – ordering variants of the Zr₇Ni₁₀ type

Abstract

The intermetallic gold compounds RE 4 Mg 3 Au 10 (RE = La, Ce, Pr) and RE 4 Cd 3 Au 10 (RE = Y, La-Nd, Sm, GdDy) were obtained from the elements through high-frequency melting in sealed niobium tubes and subsequent annealing in a muffle furnace. The new aurides crystallize with the Ca 4 In 3 Au 10 -type structure. They were characterized through Guinier powder patterns. The structures of Pr 4.46 Cd 2.54 Au 10 and Tb 4.38 Cd 2.62 Au 10 were refined from single crystal X-ray diffractometer data: Cmce, a = 1396.73 (6), b = 1009.38(3), c = 1019.51(3) pm, wR2 = 0.0423, 1281 F 2 values, 47 variables for Pr 4.46 Cd 2.54 Au 10 and a = 1362.68(3), b = 995.52(4), c = 1003.79(3) pm, wR2 = 0.0381, 1594 F 2 values, F 2 47 variables for Tb 4.38 Cd 2.62 Au 10 .The 8e sites of both crystals show substantial Cd/Pr respectively Cd/Tb mixing, indicating small homogeneity ranges for all RE 4+x Mg 3-x Au 10 and RE 4+x Cd 3-x Au 10 aurides. The gold atoms in these aurides form a pronounced two-dimensional substructure (275-327 pm Au-Au in Pr 4.46 Cd 2.54 Au 10 ) which encages the Mg1/Cd1 (coordination number 8) and RE2 (coordination number 11) atoms. These blocks are separated by the Mg2/ Cd2 and RE1 atoms with an intergrowth of Mg2/Cd2@Au 8 and RE1@Au 10 polyhedra. Temperature dependent magnetic susceptibility and specific heat measurements of Tb 4 Cd 3 Au 10 have shown antiferromagnetic ordering at a Néel temperature of 12(1) K.