Synchrotron x-ray spectroscopy studies of valence and magnetic state in europium metal to extreme pressures

TL;DR

This study uses advanced synchrotron x-ray techniques and theoretical calculations to investigate how europium metal's valence and magnetic states change under extreme pressures, revealing it remains nearly divalent and magnetic up to 87 GPa.

Contribution

It provides new experimental evidence that europium stays nearly divalent and magnetic at pressures up to 87 GPa, challenging previous assumptions.

Findings

Eu remains nearly divalent up to 87 GPa

Magnetic order persists to at least 50 GPa

Anomalous pressure dependence of M"ossbauer isomer shift

Abstract

In order to probe the changes in the valence state and magnetic properties of Eu metal under extreme pressure, x-ray absorption near-edge spectroscopy, x-ray magnetic circular dichroism and synchrotron M\"ossbauer spectroscopy experiments have been carried out. The M\"ossbauer isomer shift exhibits an anomalous pressure dependence, passing through a maximum near 20 GPa. Density functional theory has been applied to give insight into the pressure-induced changes in both Eu's electronic structure and M\"ossbauer isomer shift. Contrary to previous reports, Eu is found to remain nearly divalent to the highest pressures reached (87 GPa) with magnetic order persisting to at least 50 GPa. These results should lead to a better understanding of the nature of the superconducting state found above 75 GPa and of the sequence of structural phase transitions observed to 92 GPa.