Using resonant magnetic x-ray scattering we address the unresolved nature of the magnetic groundstate and the low-energy effective Hamiltonian of Sm2Ir2O7, a prototypical pyrochlore iridate with a finite temperature metal-insulator transition. Through a combination of elastic and inelastic measurements, we show that the magnetic ground state is an all-in all-out (AIAO) antiferromagnet. The magnon dispersion indicates significant electronic correlations and can be well-described by a minimal Hamiltonian that includes Heisenberg exchange (J=27.3(6) meV) and Dzyaloshinskii-Moriya interaction (D=4.9(3) meV), which provides a consistent description of the magnetic order and excitations. In establishing that Sm2Ir2O7 has the requisite inversion symmetry preserving AIAO magnetic groundstate, our results support the notion that pyrochlore iridates may host correlated Weyl semimetals.
@article{arxiv.1604.06401,
title = {All-in all-out magnetic order and propagating spin-waves in Sm2Ir2O7},
author = {C. Donnerer and M. C. Rahn and M. Moretti Sala and J. G. Vale and D. Pincini and J. Strempfer and M. Krisch and D. Prabhakaran and A. T. Boothroyd and D. F. McMorrow},
journal= {arXiv preprint arXiv:1604.06401},
year = {2016}
}