Role of Gd 5d-Au 5d hybridization for the magnetic properties of Au-Al-Gd quasicrystal approximants

We have studied the electronic states of magnetic Au-Al-Gd quasicrystal approximants, which exhibit different magnetic ground states at low temperatures, by orbital-selective soft and hard x-ray electron spectroscopies in the paramagnetic phase. Our results reveal that the valence electronic states vary among the Au-Al-Gd approximants with different magnetic ground states, whereas the Gd 4f electrons are localized in all of them. In particular, we find that the Gd 5d states are hybridized with the Au 5d states around the Fermi level, providing information about a local pathway for the intersite exchange interaction between the localized Gd 4f electrons. This hybridization strength varies among these samples. Our findings bring an orbital-resolved microscopic picture to the magnetism of rare-earth-based quasicrystals and approximants.