Magnetic Properties of the <i>RE</i>₂Pt₆<i>X</i>₁₅ (<i>RE</i> = Y, La–Nd, Sm, Gd–Lu; <i>X</i> = Al, Ga) Series

Abstract

The members of the RE 2 Pt 6 Al 15 ( RE = Ce–Nd, Sm, Gd–Yb) and RE 2 Pt 6 Ga 15 ( RE = Y, La–Nd, Sm, Gd–Lu) series have been synthesized from the elements via arc‐melting followed by annealing in an induction furnace. Isotypism of Ho 2 Pt 6 Al 15 with orthorhombic (3+1)D commensurately modulated Sc 2 Pt 6 Al 15 [ Cmcm ( α ,0,0)0 s 0, α = 2/3] was observed from single‐crystal diffraction data. The diffraction pattern shows the same satellite reflections pattern as the prototype, therefore the same modulated superstructure was refined. Full ordering of the Pt and Al atoms within the [Pt 6 Al 15 ] δ – polyanion was observed. The lattice parameters of the averaged hexagonal structure were refined from powder X‐ray diffraction experiments and agree well with previous reports on these compounds. The X‐ray pure polycrystalline samples of both series were studied with respect to their magnetic properties. The susceptibility data of all investigated compounds show experimental magnetic moments close to the free ion values of the RE 3+ cations and antiferro‐/ferrimagnetic ordering at low temperatures with Curie temperatures up to T C = 16.8(1) K for Gd 2 Pt 6 Ga 15 . Both, Sm 2 Pt 6 Al 15 and Sm 2 Pt 6 Ga 15 show the typical van Vleck type behavior along with antiferromagnetic ordering at a Néel temperature of T N = 4.5(1) K (Al) and ferrimagnetic ordering at T C = 6.5(1) K (Ga). Yb 2 Pt 6 Al 15 exhibits ytterbium in the trivalent oxidation state, while for Yb 2 Pt 6 Ga 15 a divalent state of the Yb atoms was observed.