Phonon spectrum of Pr2Zr2O7 and Pr2Ir2O7 as evidence of coupling of the lattice with electronic and magnetic degrees of freedom

Abstract

Magnetic materials with pyrochlore crystal structure form exotic magnetic states due to the high lattice frustration. In this work we follow the effects of coupling of the lattice and electronic and magnetic degrees of freedom in two praseodymium-based pyrochlores ${\mathrm{Pr}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ and ${\mathrm{Pr}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$. In either of these materials, the presence of magnetic interactions does not lead to magnetically ordered low temperature states; however, their electronic properties are different. A comparison of Raman phonon spectra of ${\mathrm{Pr}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ and ${\mathrm{Pr}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$ allows us to identify magnetoelastic coupling in ${\mathrm{Pr}}_{2}{\mathrm{Zr}}_{2}{\mathrm{O}}_{7}$ that elucidates its magnetic properties at intermediate temperatures and allows us to characterize phonon-electron scattering in the semimetallic ${\mathrm{Pr}}_{2}{\mathrm{Ir}}_{2}{\mathrm{O}}_{7}$. We also show that the effects of random disorder on the Raman phonon spectra is small.