111Cd- TDPAC study of pressure-induced valence transition in YbAl2

TL;DR

This study investigates pressure-induced valence changes in YbAl2 using TDPAC spectroscopy, revealing a nonlinear increase in quadrupole frequency with pressure and establishing a correlation with Yb valence.

Contribution

It provides the first detailed measurement of quadrupole interactions in YbAl2 under pressure and links these to Yb valence, offering a new method to determine valence states in Yb compounds.

Findings

Quadrupole frequency increases almost fourfold up to 80 kbar.

Linear correlation between Yb valence and electric field gradient.

Measured quadrupole frequencies in related compounds.

Abstract

The quadrupole interaction at 111Cd impurity nuclei in the intermediate-valence compound YbAl2 has been measured under pressure up to 80 kbar by the TDPAC spectroscopy. It was found that the quadrupole frequency nQ measured on the 111Cd located at the Al sites in YbAl2, varies nonlinearly and increases by almost four times with the pressure increase up to 80 kbar. A linear correlation between the mean Yb valence, derived from Yb L3 OFY-XAS and RXES measurements, and the electric field gradient (the quadrupole frequency nQ=eQVzz/h) has been observed. The quadrupole frequencies on 111Cd in the GdAl2, YbAl3, TmAl3 and CaAl2 compounds have been measured, also. The possibility of determining the valence of Yb in the Yb compounds with p-metals from the relation nQ (u(P)) = n2 + (n3 - n2) u(P) has been considered.