Structural Analysis of the Gd–Au–Al 1/1 Quasicrystal Approximant Phase across Its Composition-Driven Magnetic Property Changes

[Image: see text] Gd(14)Au(x)Al(86–x) Tsai-type 1/1 quasicrystal approximants (ACs) exhibit three magnetic orders that can be finely tuned by the valence electron concentration (e/a ratio). This parameter has been considered to be crucial for controlling the long-range magnetic order in quasicrystals (QCs) and ACs. However, the nonlinear trend of the lattice parameter as a function of Au concentration suggests that Gd(14)Au(x)Al(86–x) 1/1 ACs are not following a conventional solid solution behavior. We investigated Gd(14)Au(x)Al(86–x) samples with x values of 52, 53, 56, 61, 66, and 73 by single-crystal X-ray diffraction. Our analysis reveals that increasing Au/Al ordering with increasing x leads to distortions in the icosahedral shell built of the Gd atoms and that trends observed in the interatomic Gd–Gd distances closely correlate with the magnetic property changes across different x values. Our results demonstrate that the e/a ratio alone may be an oversimplified concept for investigating the long-range magnetic order in 1/1 ACs and QCs and that the mixing behavior of the nonmagnetic elements Au and Al plays a significant role in influencing the magnetic behavior of the Gd(14)Au(x)Al(86–x) 1/1 AC system. These findings will contribute to improved understanding towards tailoring magnetic properties in emerging materials.