We have investigated the structural, electronic, and magnetic properties of the pyrochlore iridates ${\mathrm{Eu}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ and ${\mathrm{Pr}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ using a combination of resonant elastic x-ray scattering, x-ray powder diffraction, and resonant inelastic x-ray scattering (RIXS). The structural parameters of ${\mathrm{Eu}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ 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 ($\sim 6$ to 300 K) and pressures ($\sim 0.1$ to 17 GPa) studied. We have also investigated the electronic and magnetic excitations in single-crystal samples of ${\mathrm{Eu}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ and ${\mathrm{Pr}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ using high-resolution Ir ${\mathrm{L}}_3$-edge RIXS. In spite of very different ground state properties, we find that these materials exhibit qualitatively similar excitation spectra, with crystal field excitations at $\sim 3–5$ eV, spin-orbit excitations at $\sim 0.5–1$ eV, and broad low-lying excitations below $\sim 0.15$ eV. In single-crystal samples of “Eu-rich” ${\mathrm{Eu}}_2{\mathrm{Ir}}_2{\mathrm{O}}_7$ (found to possess an actual stoichiometry of ${\mathrm{Eu}}_{2.18}{\mathrm{Ir}}_{1.82}{\mathrm{O}}_{7.06})$ we observe highly damped magnetic excitations at $\sim 45$ meV, which display significant momentum dependence. We compare these results with recent dynamical structure factor calculations.

• Received 27 October 2015
• Revised 2 June 2016

DOI:https://doi.org/10.1103/PhysRevB.94.024408