X-ray scattering study of pyrochlore iridates: Crystal structure, electronic, and magnetic excitations

Clancy, J. P.; Gretarsson, H.; Lee, E. K. H.; Tian, Di; Kim, J.; Upton, M. H.; Casa, D.; Gög, T.; Islam, Zahirul; Jeon, Byung Gu; Kim, Kee Hoon; Desgreniers, Serge; Kim, Yong Baek; Julian, S. J.

doi:10.1103/physrevb.94.024408

Cited by 53 publications

(59 citation statements)

References 57 publications

(120 reference statements)

Supporting

Mentioning

Contrasting

Order By: Relevance

“…The origin of feature C is unclear. A similar feature has been observed in the metallic Pr 2 Ir 2 O 7 and was inter- preted as paramagnetic fluctuations [20]. An alternative interpretation of feature C are lattice vibrations.…”

supporting

confidence: 67%

“…Theoretical proposals for the magnetic order with the required symmetries in pyrochlore iridates have focused on the antiferromagnetic all-in all-out (AIAO) structure, where the moments either all point towards or away from the center of the corner shared tetrahedra which form the iridium sublattice. The R 2 Ir 2 O 7 system thus offers an outstanding opportunity to study novel topological phases in the presence of electronic correlations.Despite substantial experimental effort, however, the nature of the magnetic order of the Ir ions and the effective spin Hamiltonian have remained elusive in pyrochlore iridates [13][14][15][16][17][18][19][20]. Resonant elastic x-ray scattering at the Ir L 3 edge of Eu 2 Ir 2 O 7 has found k = 0 magnetic order of undetermined type [17].…”

mentioning

confidence: 99%

“…Despite substantial experimental effort, however, the nature of the magnetic order of the Ir ions and the effective spin Hamiltonian have remained elusive in pyrochlore iridates [13][14][15][16][17][18][19][20]. Resonant elastic x-ray scattering at the Ir L 3 edge of Eu 2 Ir 2 O 7 has found k = 0 magnetic order of undetermined type [17].…”

mentioning

confidence: 99%

See 2 more Smart Citations

All-in–all-Out Magnetic Order and Propagating Spin Waves inSm2Ir2O7

et al. 2016

View full text Add to dashboard Cite

Using resonant magnetic x-ray scattering we address the unresolved nature of the magnetic groundstate and the low-energy effective Hamiltonian of Sm2Ir2O7, a prototypical pyrochlore iridate with a finite temperature metal-insulator transition. Through a combination of elastic and inelastic measurements, we show that the magnetic ground state is an all-in all-out (AIAO) antiferromagnet. The magnon dispersion indicates significant electronic correlations and can be well-described by a minimal Hamiltonian that includes Heisenberg exchange (J = 27.3(6) meV) and DzyaloshinskiiMoriya interaction (D = 4.9(3) meV), which provides a consistent description of the magnetic order and excitations. In establishing that Sm2Ir2O7 has the requisite inversion symmetry preserving AIAO magnetic groundstate, our results support the notion that pyrochlore iridates may host correlated Weyl semimetals.The search for novel electronic and magnetic phenomena has recently been fruitful in the correlated, strong spin-orbit coupling regime [1][2][3][4]. The family of pyrochlore iridates, R 2 Ir 2 O 7 (where R is a rare-earth element), has received much interest since the prediction of topologically non-trivial states, most prominently the Weyl semimetal (WSM) [5][6][7][8]. This is motivated by the observation of metal-insulator transitions as a function of temperature and rare-earth ion radius that occur concomitantly with the onset of magnetic order [9][10][11][12]. As magnetic order breaks time-reversal symmetry, the WSM state in these correlated materials requires the preservation of inversion symmetry, a scenario distinct from the weakly correlated limit where the opposite is true. Theoretical proposals for the magnetic order with the required symmetries in pyrochlore iridates have focused on the antiferromagnetic all-in all-out (AIAO) structure, where the moments either all point towards or away from the center of the corner shared tetrahedra which form the iridium sublattice. The R 2 Ir 2 O 7 system thus offers an outstanding opportunity to study novel topological phases in the presence of electronic correlations.Despite substantial experimental effort, however, the nature of the magnetic order of the Ir ions and the effective spin Hamiltonian have remained elusive in pyrochlore iridates [13][14][15][16][17][18][19][20]. Resonant elastic x-ray scattering at the Ir L 3 edge of Eu 2 Ir 2 O 7 has found k = 0 magnetic order of undetermined type [17]. Due to the small magnetic moment of the Ir ion and its high neutron absorption, neutron diffraction has only been successful in studying the rare-earth sublattice. For R = Tb and Nd rare-earths, AIAO magnetic order was found, which has been argued to provide indirect evidence for identical ordering on the Ir lattice [14,19]. An upper limit on the size of the ordered Ir moment was placed at 0.2 µ B (Tb) [19] and 0.5 µ B (Y) [15].Here, we use resonant elastic and inelastic x-ray scattering (REXS and RIXS) at the Ir L 3 edge to reveal the nature of the magnetic order and excitations of the pyroch...

show abstract

supporting

confidence: 67%

mentioning

confidence: 99%

See 1 more Smart Citation

All-in–all-Out Magnetic Order and Propagating Spin Waves inSm2Ir2O7

et al. 2016

View full text Add to dashboard Cite

show abstract

“…Resonant inelastic X-ray scattering has observed such a feature for Eu 2 Ir 2 O 7 , Pr 2 Ir 2 O 7 , and Sm 2 Ir 2 O 7 8, 46 , though its appearance is likely complicated by other excitations. This feature unexpectedly extends to higher energy for Pr 2 Ir 2 O 7 than Eu 2 Ir 2 O 7 8 , as a result of the larger cationic ratio of Pr/Ir, inducing more disorder for Pr 2 Ir 2 O 7 .…”

Section: Discussionmentioning

confidence: 99%

“…Additional disorder, such as A / B site-mixing is not uncommon 5–8 , and can lead to the weberite structure 9 , unless optimal cation ordering occurs. Lastly, polyhedral distortions can also occur, where the tetrahedral corners move in or out.…”

Section: Introductionmentioning

confidence: 99%

Universal geometric frustration in pyrochlores

et al. 2018

View full text Add to dashboard Cite

Materials with the pyrochlore/fluorite structure have diverse technological applications, from magnetism to nuclear waste disposal. Here we report the observation of structural instability present in the pyrochlores A2Zr2O6Oʹ (A = Pr, La) and Yb2Ti2O6Oʹ, that exists despite ideal stoichiometry, ideal cation-ordering, the absence of lone pair effects, and a lack of magnetic order. Though these materials appear to have good long-range order, local structure probes find displacements, of the order of 0.01 nm, within the pyrochlore framework. The pattern of displacements of the A2Oʹ sublattice mimics the entropically-driven fluxional motions characteristic of and well-known in the silica mineral β-cristobalite. The universality of such displacements within the pyrochlore structure adds to the known structural diversity and explains the extreme sensitivity to composition found in quantum spin ices and the lack of ferroelectric behavior in pyrochlores.

show abstract