X-ray scattering study of pyrochlore iridates: crystal structure, electronic and magnetic excitations

TL;DR

This study investigates the structural, electronic, and magnetic properties of pyrochlore iridates Eu2Ir2O7 and Pr2Ir2O7 using advanced x-ray scattering techniques, revealing no crystal symmetry change and similar excitation spectra despite different ground states.

Contribution

The paper provides a comprehensive analysis of Eu2Ir2O7 and Pr2Ir2O7, showing their excitation spectra are qualitatively similar and offering insights into their magnetic excitations and structural stability.

Findings

No crystal symmetry change over temperature and pressure range.

Similar excitation spectra in Eu2Ir2O7 and Pr2Ir2O7 despite different ground states.

Observation of highly damped magnetic excitations at ~45 meV in Eu2Ir2O7.

Abstract

We have investigated the structural, electronic, and magnetic properties of the pyrochlore iridates Eu2Ir2O7 and Pr2Ir2O7 using a combination of resonant elastic x-ray scattering, x-ray powder diffraction, and resonant inelastic x-ray scattering (RIXS). The structural parameters of Eu2Ir2O7 have been examined as a function of temperature and applied pressure, with a particular emphasis on regions of the phase diagram where electronic and magnetic phase transitions have been reported. We find no evidence of crystal symmetry change over the range of temperatures (~6 to 300 K) and pressures (~0.1 to 17 GPa) studied. We have also investigated the electronic and magnetic excitations in single crystal samples of Eu2Ir2O7 and Pr2Ir2O7 using high resolution Ir L3-edge RIXS. In spite of very different ground state properties, we find these materials exhibit qualitatively similar excitation spectra, with crystal field excitations at ~3-5 eV, spin-orbit excitations at ~0.5-1 eV, and broad low-lying excitations below ~0.15 eV. In Eu2Ir2O7 we observe highly damped magnetic excitations at ~45 meV, which display significant momentum dependence. We compare these results with recent dynamical structure factor calculations.