Electronic structures of UX3 ( X=Al , Ga, and In) studied by photoelectron spectroscopy

The electronic structures of $\mathrm{U}{X}₃$ ($X=\mathrm{Al}, \mathrm{Ga}$, and $\mathrm{In}$) were studied by photoelectron spectroscopy to understand the relationship between their electronic structures and magnetic properties. The band structures and Fermi surfaces of ${\mathrm{UAl}}₃$ and ${\mathrm{UGa}}₃$ were revealed experimentally by angle-resolved photoelectron spectroscopy (ARPES), and they were compared with the result of band-structure calculations. The topologies of the Fermi surfaces and the band structures of ${\mathrm{UAl}}₃$ and ${\mathrm{UGa}}₃$ were explained reasonably well by the calculation, although bands near the Fermi level (${E}_{\mathrm{F}}$) were renormalized owing to the finite electron correlation effect. The topologies of the Fermi surfaces of ${\mathrm{UAl}}₃$ and ${\mathrm{UGa}}₃$ are very similar to each other, except for some minor differences. Such minor differences in their Fermi surface or electron correlation effect might take an essential role in their different magnetic properties. No significant changes were observed between the ARPES spectra of ${\mathrm{UGa}}₃$ in the paramagnetic and antiferromagnetic phases, suggesting that ${\mathrm{UGa}}₃$ is an itinerant weak antiferromagnet. The effect of chemical pressure on the electronic structures of $\mathrm{U}{X}₃$ compounds was also studied by utilizing the smaller lattice constants of ${\mathrm{UAl}}₃$ and ${\mathrm{UGa}}₃$ than that of ${\mathrm{UIn}}₃$. The valence band spectrum of ${\mathrm{UIn}}₃$ is accompanied by a satellitelike structure on the high-binding-energy side. The core-level spectrum of ${\mathrm{UIn}}₃$ is also qualitatively different from those of ${\mathrm{UAl}}₃$ and ${\mathrm{UGa}}₃$. These findings suggest that the $\mathrm{U}\phantom{\rule{4pt}{0ex}}5f$ states in ${\mathrm{UIn}}₃$ are more localized than those in ${\mathrm{UAl}}₃$ and ${\mathrm{UGa}}₃$.