2D crystal structure and anisotropic magnetism of GdAu 6.75-x Al 0.5+x (x ≈ 0.54).

Exploration of the gold-rich part of the ternary Gd-Au-Al system afforded the intermetallic compound GdAu _6.75-x Al _0.5+x (x ≈ 0.54) which was structurally characterized by single crystal X-ray diffraction (Pnma, a = 18.7847(4) Å, b = 23.8208(5) Å, c = 5.3010(1) Å). GdAu _6.75-x Al _0.5+x crystallizes in a previously unknown structure type featuring layers of Gd ₂ (Au, Al) ₂₉ and Gd ₂ (Au, Al) ₂₈ clusters which are arranged as in a close-packing parallel to the ac plane. The Gd substructure corresponds to slightly corrugated 3 ⁶ nets (d _Gd-Gd  = 5.30-5.41 Å) which are stacked on top of each other along the b direction with alternating short (5.4, 5.6 Å, within layers) and long distances (6.4 Å, between layers). The title compound has been discussed with respect to a quasicrystal approximant (1/1 AC) GdAu _5.3 Al in the same system. The magnetic properties of GdAu _6.75-x Al _0.5+x were found to be reminiscent to those of some ternary ACs, with sharp peaks in the temperature dependent magnetization, and metamagnetic-like transitions. The material becomes antiferromagnetic below 25 K; magnetometry results suggest that the antiferromagnetic state is composed of ferromagnetic ac planes, coupled antiferromagnetically along the b direction.
(© 2022. The Author(s).)