paper

Dual nature of 5 $f$ electrons in the isostructural UM $_{2}$ Si $_{2}$ family: from antiferro- to Pauli paramagnetism via hidden order

arXiv:2004.13419 · doi:10.1073/pnas.2005701117

Abstract

Using inelastic x-ray scattering beyond the dipole limit and hard x-ray photoelectron spectroscopy we establish the dual nature of the U $5 f$ electrons in UM $_{2}$ Si $_{2}$ (M = Pd, Ni, Ru, Fe), regardless of their degree of delocalization. We have observed that the compounds have in common a local atomic-like state that is well described by the U $5 f^{2}$ configuration with the $I^_{1}^{(1)}$ and $I^_{2}$ quasi-doublet symmetry. The amount of the U 5 $f^{3}$ configuration, however, varies considerably across the UM $_{2}$ Si $_{2}$ series, indicating an increase of U5 $f$ itineracy in going from M=Pd to Ni to Ru, and to the Fe compound. The identified electronic states explain the formation of the very large ordered magnetic moments in UPd $_{2}$ Si $_{2}$ and UNi $_{2}$ Si $_{2}$ , the availability of orbital degrees of freedom needed for the hidden order in URu $_{2}$ Si $_{2}$ to occur, as well as the appearance of Pauli paramagnetism in UFe $_{2}$ Si $_{2}$ . A unified and systematic picture of the U $M_{2}$ Si $_{2}$ compounds may now be drawn, thereby providing suggestions for new experiments to induce hidden order and/or superconductivity in U compounds with the tetragonal body-centered ThCr $_{2}$ Si $_{2}$ structure.

Dual nature of 5f electrons in the isostructural UM2​Si2​ family: from antiferro- to Pauli paramagnetism via hidden order

Abstract

Dual nature of 5 $f$ electrons in the isostructural UM $_{2}$ Si $_{2}$ family: from antiferro- to Pauli paramagnetism via hidden order