RE4TAl (RE = Y, Sm, Gd-Tm, Lu; T = Pd, Pt) - Synthesis and magnetism of new aluminum representatives with the Gd4RhIn type structure

Sixteen new intermetallic aluminum compounds with RE4TAl (RE = Y, Sm, Gd-Tm, Lu; T = Pd, Pt) composition have been prepared by arc-melting of the elements followed by subsequent annealing. The samples were characterized by powder X-ray diffraction. All compounds crystallize isostructural in the cubic Gd4RhIn type structure (F4¯3m) with lattice parameters ranging from a = 1369-1323 pm for Pd and a = 1377-1323 pm for Pt. In the crystal structure, the transition metal atoms have a trigonal prismatic rare earth coordination. Condensation of these T@RE6 prisms leads to a three-dimensional network in which large voids are present that are filled by tetrahedral Al4 entities. The aluminum atoms themselves have twelve nearest neighbors (3 × Al and 9 × RE) in a slightly distorted icosahedral coordination. For the compounds of the Pt series the magnetic properties have been investigated by means of magnetic susceptibility measurements. Gd4PtAl and Tb4PtAl order antiferromagnetically at Néel temperatures of TN = 63.8(1) and 45.9(1) K, while Dy4PtAl and Ho4PtAl order ferromagnetically with Curie temperatures TC = 32.6(1) and 23.8(1) K. For the Pd series finally, the REAl impurities dominate, hence magnetic measurements were not conducted.