Structural and magnetic investigations of the pseudo-ternary RE 2 TAl3 series (RE=Sc, Y, La–Nd, Sm, Gd–Lu; T=Ru, Rh, Ir) – size dependent formation of two different structure types

Abstract

Abstract Several rare earth metal containing pseudo-ternary compounds in the RE 2 TAl3 series (RE=Sc, Y, La–Nd, Sm, Gd–Lu; T=Ru, Rh, Ir) have been synthesized from the elements by arc-melting or in tantalum capsules. Within the Rh series, the compounds with RE=La–Nd crystallize in the cubic MgCu2-type (Fd3̅m) structure. For Sm besides the cubic Laves phase also the hexagonal Laves phase (MgZn2 type, P63/mmc) is found. For the remaining compounds of both series, also the hexagonal MgZn2-type structure is observed. The structures of Ho2Ru0.96(1)Al3.04(1) (a=547.4(1), c=875.7(1) pm, wR=0.0397, 201 F 2 values, 13 variables), Sc2Rh1.01(1)Al2.99(1) (a=528.0(1), c=852.8(1) pm, wR=0.0228, 184 F 2 values, 13 variables), Ho2Rh1.00(1)Al3.00(1) (a=546.5(1), c=873.8(1) pm, wR=0.0590, 222 F 2 values, 13 variables) and Tb2Ir1.06(1)Al2.94(1) (a=550.8(1), c=870.0(1) pm, wR=0.0743, 221 F 2 values, 13 variables) have been refined from single-crystal data, indicating T/Al mixing on both crystallographic Zn sites of the aristotype. The Sc, Y, La and Lu containing compounds exhibit Pauli-paramagnetic behavior, while the other compounds show paramagnetism, in line with the rare earth atoms in the trivalent oxidation state. Ferro- and antiferromagnetic ordering up to T C=50.2(1) K for Gd2RhAl3 is observed, while Sm2RuAl3 shows van Vleck paramagnetism and Yb2RuAl3, finally, exhibits only partially trivalent Yb atoms, evident from a reduced magnetic moment and increased lattice parameters.