Singlet magnetism in intermetallic<mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"><mml:msub><mml:mi>UGa</mml:mi><mml:mn>2</mml:mn></mml:msub></mml:math>unveiled by inelastic x-ray scattering
Andrea Marino, Martin Sundermann, Denise S. Christovam, Andrea Amorese, C. F. Chang, Paulius Dolmantas, Ayman Said, H. Gretarsson, B. Keimer, M. W. Haverkort, А. В. Андреев, L. Havela, Peter Thalmeier, L. H. Tjeng, A. Severing
Abstract
Using high resolution tender x-ray resonant inelastic scattering and hard x-ray nonresonant inelastic scattering beyond the dipole limit we were able to detect electronic excitations in intermetallic ${\mathrm{UGa}}_{2}$ that are highly atomic in nature. Analysis of the spectral lineshape reveals that the local $5{f}^{2}$ 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 ${\mathrm{\ensuremath{\Gamma}}}_{1}$ singlet and/or ${\mathrm{\ensuremath{\Gamma}}}_{6}$ doublet symmetry. With the ordered moment in the $ab$ plane, we infer that the magnetism originates from the higher lying ${\mathrm{\ensuremath{\Gamma}}}_{6}$ doublet being mixed with the ${\mathrm{\ensuremath{\Gamma}}}_{1}$ singlet due to intersite exchange, qualifying ${\mathrm{UGa}}_{2}$ to be a true quantum magnet. The ability to observe atomic excitations is crucial to resolve the ongoing debate about the degree of localization versus itineracy in U intermetallics.