Selective probing of magnetic order on Tb and Ir sites in stuffed Tb₂Ir₂O₇ using resonant x-ray scattering

Abstract

We study the magnetic structure of the "stuffed" (Tb-rich) pyrochlore iridate Tb2+xIr2−xO7−y, 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 T Ir N ∼ 71 K, consistent with the expected signal of all-in all-out (AIAO) magnetic order. Using a single-ion model to calculate REXS crosssections, we estimate an ordered magnetic moment of µ Ir 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 T Ir N = 130 K and µ Ir 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.

Asymmetric Magnetization Reversal Behaviors Driven by Exchange Coupling between All-in-All-out Magnetic Domains and Domain Walls in a Eu2Ir2O7 Single Crystal

“…Since chemical off-stoichiometry in Eu 2+ x Ir 2– x O 7– y cause the nonmagnetic Eu 3+ ions stuffing onto Ir sites or antisite Eu/Ir occupations, , the introduced nonmagnetic defects will dilute the Ir 4+ moments, leading to the instability of AIAO order and reduced net FM components within DWs. These behaviors are consistent with recent resonant X-ray scattering on Tb 2+ x Ir 2– x O 7– y single crystals, where off-stoichiometry reduces both T N and effective moments of Ir 4+ sublattices. On the other side, less magnetic disorders in stoichiometric crystals help to stabilize the AIAO domain state and related DWs, responsible for the enhanced ferromagnetism.…”

“…The most stoichiometric crystal exhibits the largest H EB , M shift , and coercive field ( H C ) in all measured temperatures (Figure a–c), indicative of its strongest exchange coupling between the AIAO domain and its DWs. Considering the nonmagnetic dilution effect on Ir 4+ sublattices in off-stoichiometric Eu 2+ x Ir 2– x O 7– y , , the reduced FM components in DWs and concomitant unstable AIAO order will weaken the FM/AFM exchange coupling, producing smaller EB effects in off-stoichiometric crystals. As shown in Figure c, H C shows nonmonotonic temperature dependence with maxima at temperature ( T p ).…”

Imprint of charge and oxygen orders on Dy ions in DyBa$_2$Cu$_3$O$_{6+x}$ thin films probed by resonant x-ray scattering

“…5 (a)). A similar dependence of the RXS signal on the field strength has been observed by Donnerer et al 25 in Tb 2 Ir 2 O 7 . Finally, we observed that modifying the field direction from α ∼ 45 • towards a fully out-of-plane configuration, i.e.…”

“…The correlation lengths at 5 K are ∼ 27 Å and ∼ 32 Å for the induced ortho and CDW orders, respectively. In various transition metal oxides 24,25 and other multinary rare-earth containing systems, such as the rare-earth tritellurides 26 or synthetic multilayer systems 27 , the formation of induced order on the rareearth sublattice has already been observed. Likewise, in DyBCO, the temperature-dependent resonant scattering intensity at the Dy edge decays quickly with temperature, reflecting the temperature-dependent susceptibility of the Dy sublattice (Fig.…”

Structural, magnetic and magnetocaloric effect of pyrochlore iridate Er2Ir2O7

“…Pyrochlore iridates of formula A 2 B 2 O 7 (A= rare Earth elements; and B= Ir) are one of the materials with a significant magnetic frustration owing to Coulomb correlation and spin-orbit coupling [25][26][27]. Among these materials we find: Pr 2 Ir 2 O 7 , Tb 2 Ir 2 O 7 , Eu 2 Ir 2 O 7 , Y 2 Ir 2−x Cr x O 7 [28][29][30], etc According to the findings on these materials, the lanthanides A and their interactions with the moments B = Ir frequently result in intriguing physical properties. These materials have been used in a variety of applications, including magnetic refrigeration.…”