Ferromagnetic 2/1 quasicrystal approximants
Kazuki Inagaki, Shintaro Suzuki, Asuka Ishikawa, Takafumi Tsugawa, F. Aya, Tsunetomo Yamada, K. Tokiwa, Tetsuya Takeuchi, Ryuji Tamura
Abstract
The existence of various magnetic orders has recently been established in the Tsai-type 1/1 approximant Au-Al-Gd by variation of the electron-per-atom (e/a) ratio [Ishikawa et al. Phys. Rev. B 98, 220403(R) (2018)]. Here, we report ferromagnetic (FM) 2/1 quasicrystal approximants and show that the magnetic order of higher-order approximants can be tailored starting from known magnetic 1/1 approximants. The (Au,Cu)-(Al,In)-$R\phantom{\rule{4pt}{0ex}}(R=\mathrm{Gd},\mathrm{Tb})2$/1 approximants are synthesized by the simultaneous substitution of isovalent elements Cu and In for Au and Al, respectively, to the FM Au-Al-$R\phantom{\rule{4pt}{0ex}}(R=\mathrm{Gd},\mathrm{Tb})1$/1 approximants with $e/a=1.74$. Both the (Au,Cu)-(Al,In)-$R\phantom{\rule{4pt}{0ex}}(R=\mathrm{Gd},\mathrm{Tb})2$/1 approximants exhibit a FM transition at significantly high Curie temperatures of ${T}_{\mathrm{C}}=30.0$ and 15.3 K, respectively. Therefore, this method of isovalent substitution will also enable the realization of a variety of magnetic orders for the 2/1 approximant by variation of the e/a ratio. Such isovalent substitution may also stabilize magnetic quasicrystals for a given e/a ratio, which would lead to the realization of the long-range magnetic order in quasicrystals.