Determination of long-range all-in-all-out ordering of Ir4+ moments in a pyrochlore iridate Eu2Ir2O7 by resonant x-ray diffraction

The pyrochlore-type iridium oxide Eu2Ir2O7 exhibits a metal-insulator transition at 120 K, accompanied by magnetic ordering. We used x-ray diffraction measurements with photon energies near the iridium L-3 absorption edge to analyze a single crystal to investigate the arrangement of Ir4+ magnetic moments. Resonant magnetic scattering at (4n + 2 0 0) was observed in the insulating phase, providing direct evidence of long-range ordering of Ir4+ magnetic moments with a propagation vector of q = (000). Our single-crystal structure analysis revealed that the lattice retains its face-centered-cubic structure across the metal-insulator transition, indicating all-in-all-out magnetic order, where all the magnetic moments on the four vertices of each Ir tetrahedron point inward or outward. DOI: 10.1103/PhysRevB.87.100403