First-principles studies of the unconventional spin-phonon coupling mediated by spin-orbit coupling in pyrochlore Cd2Os2O7

Abstract

We perform systematic first-principles calculations to investigate the spin-phonon coupling (SPC) mediated by spin-orbit coupling in pyrochlore ${\mathrm{Cd}}_{2}{\mathrm{Os}}_{2}{\mathrm{O}}_{7}$ which has the peculiar all-in-all-out noncollinear magnetic ground state. A large SPC coefficient up to $34\phantom{\rule{0.28em}{0ex}}\mathrm{c}{\mathrm{m}}^{--1}$ is found, showing the potential of using this material in thermal spin devices. We further split the SPC coefficients to contributions from symmetric exchange interaction, Dzyaloshinskii-Moriya interaction (DMI), and the single ion anisotropy. Unlike what was assumed in previous studies, the DMI contributions are rather important for most modes. These results provide insights for the understanding of the SPC in $5d$ transition metal oxides and useful guidance for the search of excellent spin caloritronic materials.