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

2016; American Physical Society; Volume: 94; Issue: 22 Linguagem: Inglês

10.1103/physrevb.94.220407

2469-9977

Stuart Calder, Jong‐Woo Kim, A. E. Taylor, M. H. Upton, D. Casa, Guixin Cao, David Mandrus, M. D. Lumsden, A. D. Christianson,

Physics of Superconductivity and Magnetism

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 J=1/2 moments diluted.