Eight years since the discovery of the binary antiferromagnetic (AFM) quasicrystal approximants $\mathrm{C}{\mathrm{d}}_{6}R$ [R. Tamura et al., Phys. Rev. B 82, 220201 (2010)], we report the observation of an AFM transition in quasicrystal approximants Au-Al-R ($R=\mathrm{Gd}$ and Tb), which represent examples of AFM in ternary quasicrystal approximants. Magnetic susceptibility, magnetization, and specific heat coherently show that the Au-Al-R ($R=\mathrm{Gd}$ and Tb) approximants undergo an AFM transition at $T_{\mathrm{N}}=9.4$ and 11.8 K, respectively. The AFM transitions are found near the phase boundary of the wide single-phase region where the chemical disorder is substantially low. This finding of ternary AFM approximants has far deeper implications compared with that of the binary AFM approximants: It now indicates the possibility to synthesize new AFM approximants in many other systems by the appropriate replacement of Cd with two other elements, and thus enables exploration of various magnetic orders over AFM spin icosahedra in solids, in particular, their evolution as a function of the electron-per-atom (e/a) ratio. Moreover, the finding provides us a missing route to synthesize an AFM quasicrystal by similar composition tuning.

• Received 17 December 2017
• Revised 28 September 2018

DOI:https://doi.org/10.1103/PhysRevB.98.220403