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  Donnerer, C.; Rahn, M.; Schierle, E.; Perry, R.; Veiga, L.; Nisbet, G.; Collins, S.; Prabhakaran, D.; Boothroyd, A.; McMorrow, D.: Selective probing of magnetic order on Tb and Ir sites in stuffed Tb₂Ir₂O₇ using resonant x-ray scattering. Journal of Physics: Condensed Matter 31 (2019), p. 344001/1-8

10.1088/1361-648X/ab2217
Open Access Version

Abstract:
We study the magnetic structure of the ‘stuffed’ (Tb-rich) pyrochlore iridate Tb2+xIr2−xO7−y (x ∼ 0.18), using resonant elastic x-ray scattering (REXS). In order to disentangle contributions from Tb and Ir magnetic sublattices, experiments were performed at the Ir L3 and Tb M5 edges, which provide selective sensitivity to Ir 5d and Tb 4f magnetic moments, respectively. At the Ir L3 edge, we found the onset of long-range k = 0 magnetic order below TIr N  71 K, consistent with the expected signal of all-in all-out (AIAO) magnetic order. Using a single-ion model to calculate REXS cross-sections, we estimate an ordered magnetic moment of μIr 5d  0.34(3) μB at 5 K. At the Tb M5 edge, long-range k = 0 magnetic order appeared below ∼40 K, also consistent with an AIAO magnetic structure on the Tb site. Additional insight into the magnetism of the Tb sublattice is gleaned from measurements at the M5 edge in applied magnetic fields up to 6 T, which is found to completely suppress the Tb AIAO magnetic order. In zero applied field, the observed gradual onset of the Tb sublattice magnetisation with temperature suggests that it is induced by the magnetic order on the Ir site. The persistence of AIAO magnetic order, despite the greatly reduced ordering temperature and moment size compared to stoichiometric Tb2Ir2O7, for which TIr N = 130 K and μIr 5d = 0.56 μB, indicates that stuffing could be a viable means of tuning the strength of electronic correlations, thereby potentially offering a new strategy to achieve topologically non-trivial band crossings in pyrochlore iridates.