Synthesis and magnetic properties of the extended RE4Pd9Al24 series (RE = Sc, Y, Ce-Nd, Sm, Gd-Lu)

The existing RE4Pd9Al24 series (triclinic, space group P (1) over bar) with RE = Gd-Tm has been extended to the rare earth elements Sc, Y, Ce-Nd, Sm, Yb and Lu. The samples were synthesized from the elements via arc-melting followed by annealing. Phase-purity was checked by powder X-ray diffraction experiments, which were also utilized to refine the lattice parameters. The structure can be described as composed of layers with a stacking of [PtAl2] (A) and [RE2Al3] (B) slabs in an ABAAB sequence. As two different structure types (P (1) over bar and R (3) over barm) have been reported for this composition, a group-subgroup scheme using the Barnighausen formalism has been established in order to link the two. The magnetic properties of the X-ray-pure samples were investigated by susceptibility and magnetization measurements. Gd4Pd9Al24 shows the highest transition temperature to antiferromagnetism of T-N = 22.0(1) K, however, a broad feature is observed. This is in line with a low-dimensional ordering caused by the layer-like structure and the flat honeycomb arrangement of the Gd atoms.