We use resonant elastic and inelastic x-ray scattering at the Ir-L3 edge to study the doping-dependent magnetic order, magnetic excitations, and spin-orbit excitons in the electron-doped bilayer iridate (Sr1−xLax)3Ir2O7 (0 ≤ x ≤ 0.065). With increasing doping x, the three-dimensional long range antiferromagnetic order is gradually suppressed and evolves into a three-dimensional short range order across the insulator-to-metal transition from x = 0 to 0.05, followed by a transition to two-dimensional short range order between x = 0.05 and 0.065. Because of the interactions between the Jeff = 1/2 pseudospins and the emergent itinerant electrons, magnetic excitations undergo damping, anisotropic softening, and gap collapse, accompanied by weakly doping-dependent spin-orbit excitons. Therefore, we conclude that electron doping suppresses the magnetic anisotropy and interlayer couplings and drives (Sr1−xLax)3Ir2O7 into a correlated metallic state with two-dimensional short range antiferromagnetic order. Strong antiferromagnetic fluctuations of the Jeff = 1/2 moments persist deep in this correlated metallic state, with the magnon gap strongly suppressed.
Digital Object Identifier (DOI)
Xingye Lu acknowledges financial support from the European Community’s Seventh Framework Programme (FP7/2007–2013) under Grant agreement No. 290605 (COFUND: PSI-FELLOW). G. Cao acknowledges support by the US National Science Foundation via Grants No. DMR-1265162 and No. DMR-1712101. The work used Sector 27 of the Advanced Photon Source, a U.S. Department of Energy (DOE) Office of Science User Facility operated for the DOE Office of Science by Argonne National Laboratory under Contract No. DE-AC02-06CH11357.
See Supplemental Material at http://link.aps.org/supplemental/10.1103/PhysRevLett.118.027202 for details, which includes Refs. [40–49].
Lu, Xingye; McNally, D. E.; Sala, M. Moretti; Terzic, Jsaminka; Upton, M. H.; Casa, D.; Ingold, G.; Cao, Gang; and Schmitt, T., "Doping Evolution of Magnetic Order and Magnetic Excitations in (Sr1-xLax)3Ir2O7" (2017). Physics and Astronomy Faculty Publications. 532.