Singlet magnetism in intermetallic UGa${}_2$ unveiled by inelastic x-ray scattering

Abstract

Using high resolution tender-x-ray resonant inelastic scattering and hard-x-ray non-resonant inelastic scattering beyond the dipole limit we were able to detect electronic excitations in intermetallic UGa${}_2$ that are highly atomic in nature. Analysis of the spectral lineshape reveals that the local $5f^2$ configuration characterizes the correlated nature of this ferromagnet. The orientation and directional dependence of the spectra indicate that the ground state is made of the ${\Gamma }_1$ singlet and/or ${\Gamma }_6$ doublet symmetry. With the ordered moment in the $ab$ plane, we infer that the magnetism originates from the higher lying ${\Gamma }_6$ doublet being mixed with the ${\Gamma }_1$ singlet due to inter-site exchange, qualifying UGa${}_2$ to be a true quantum magnet. The ability to observe atomic excitations is crucial to resolve the on-going debate about the degree of localization versus itineracy in U intermetallics.

arXiv comment9 pages, 7 figures

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