Strong anisotropy within a Heisenberg model in the Jeff= 12 insulating state of Sr2Ir0.8Ru0.2 O4

S. Calder, J. W. Kim, A. E. Taylor, M. H. Upton, D. Casa, Guixin Cao, D. Mandrus, M. D. Lumsden, A. D. Christianson

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    Abstract

    The dispersive magnetic excitations in Sr2IrO4 have previously been well described within an isospin-1/2 Heisenberg model on a square lattice that revealed parallels with La2CuO4. Here we investigate the inelastic spectra of Sr2Ir0.8Ru0.2O4 with resonant inelastic x-ray scattering (RIXS) at the Ir L3 edge. The results are well described using linear spin-wave theory within a similar Heisenberg model applicable to Sr2IrO4; however, the disorder induced by the substitution of 20%Ir4+ ions for Ru4+ removes longer range exchange interactions. A large spin gap (40 meV) is measured indicating strong anisotropy from spin-orbit coupling that is manifest due to the altered magnetic structure in Sr2Ir0.8Ru0.2O4 with c-axis aligned moments compared to the basal plane moments in the parent. Collectively the results indicate the robustness of a Heisenberg model description even when the magnetic structure is altered and the Jeff=1/2 moments are diluted.

    Original languageEnglish
    Article number220407
    JournalPhysical Review B
    Volume94
    Issue number22
    DOIs
    StatePublished - Dec 28 2016

    Funding

    This research used resources 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. A portion of this research used resources at the High Flux Isotope Reactor and Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. D.M. acknowledges support from the U.S. Department of Energy, Office of Science, Basic Energy Sciences, Materials Sciences and Engineering Division.

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