Pressure-Induced f-Electron Delocalization in the U-Based Strongly Correlated Compounds UPd3 and UPd2Al3: Resonant Inelastic X-Ray Scattering and First-Principles Calculations

We have measured the uranium L3 absorption and resonant emission spectra in the localized magnetic compound UPd3 and heavy fermion UPd2Al3 as a function of pressure. The spectral line shape of the absorption edge is found to vary rapidly in UPd2Al3 with a notable broadening of the white line above the structural transition around 25 GPa while it shows a more gradual variation in UPd3 over the considered pressure range 0–40 GPa, indicating different responses of the f-d electrons to the compressed lattice in the two compounds. The U L3 absorption spectra in both UPd3 and UPd2Al3 and their pressure dependence were further simulated via first-principles band calculations within the linear muffin-tin orbital approach. The calculations reproduce the main features of the experimental absorption edges. The calculated pressure dependence of the f charge reveals a stronger localization of the f electrons in UPd3 which shows a remarkably stable valency under pressure, close the nominal value of 4. On the contrary, our results point to a mixed valent U4− ground state in UPd2Al3 at ambient conditions, evolving into a U4+ or possibly U4+ configuration at high pressure. The f-electron delocalization could be responsible for the known structural transition in UPd2Al3.

RUEFF J.P.;  RAYMOND S.;  YARESKO A.;  BRAITHWAITE D.;  LEININGER Ph.;  VANKO G.;  HUXLEY A.;  REBIZANT Jean;  SATO N.; 

2007-08-27

AMERICAN PHYSICAL SOC

JRC38233

https://publications.jrc.ec.europa.eu/repository/handle/JRC38233,   

10.1103/PhysRevB.76.085113,