Interplay between structural, magnetic, and electronic states in the pyrochlore iridate Eu2Ir2O7

DOI: 10.1103/PhysRevB.105.134421

Authors: Manjil Das (Indian Association for the Cultivation of Science) , Sayantika Bhowal (Indian Association for the Cultivation of Science; ETH Zurich) , Jhuma Sannigrahi (Indian Institute of Technology Goa) , Abhisek Bandyopadhyay (Indian Institute of Science Education and Research) , Anupam Banerjee (Indian Association for the Cultivation of Science) , Giannantonio Cibin (Diamond Light Source) , Dmitry Khalyavin (ISIS Neutron and Muon Source) , Niladri Banerjee (Loughborough University) , Devashibhai Adroja (ISIS Neutron and Muon Source; University of Johannesburg) , Indra Dasgupta (Indian Association for the Cultivation of Science) , Subham Majumdar (Indian Association for the Cultivation of Science)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Physical Review B , VOL 105

State: Published (Approved)
Published: April 2022
Diamond Proposal Number(s): 17752

Abstract: We address the concomitant metal-insulator transition (MIT) and antiferromagnetic ordering in the novel pyrochlore iridate Eu 2 Ir 2 O 7 by combining x-ray absorption spectroscopy, x-ray and neutron diffractions, and density functional theory (DFT)-based calculations. The temperature dependent powder x-ray diffraction clearly rules out any change in the lattice symmetry below the MIT, nevertheless a clear anomaly in the Ir-O-Ir bond angle and Ir-O bond length is evident at the onset of MIT. From the x-ray absorption near edge structure (XANES) spectroscopic study of Ir- L 3 and L 2 edges, the effective spin-orbit coupling is found to be intermediate, at least quite far from the strong atomic spin-orbit coupling limit. Powder neutron diffraction measurement is in line with an all-in-all-out magnetic structure of the Ir-tetrahedra in this compound, which is quite common among rare-earth pyrochlore iridates. The sharp change in the Ir-O-Ir bond angle around the MIT possibly arises from the exchange striction mechanism, which favors an enhanced electron correlation via weakening of Ir-Ir orbital overlap and an insulating phase below T M I . The theoretical calculations indicate an insulating state for shorter bond angle validating the experimental observation. Our DFT calculations show a possibility of intriguing topological phase below a critical value of the Ir-O distance, which is shorter than the experimentally observed bond length. Therefore, a topological state may be realized in bulk Eu 2 Ir 2 O 7 sample if the Ir-O bond length can be reduced by the application of sufficient external pressure.

Journal Keywords: First-principles calculations; Metal-insulator transition; Spin-orbit coupling; Polycrystalline materials; Neutron diffraction; X-ray absorption fine structure spectroscopy; X-ray absorption near-edge spectroscopy; X-ray diffraction

Diamond Keywords: Antiferromagnetism

Subject Areas: Materials, Physics


Instruments: B18-Core EXAFS

Other Facilities: P21.1 at PETRA III; WISH at ISIS

Added On: 21/04/2022 10:40

Discipline Tags:

Quantum Materials Hard condensed matter - electronic properties Physics Hard condensed matter - structures Magnetism Materials Science

Technical Tags:

Spectroscopy X-ray Absorption Spectroscopy (XAS) Extended X-ray Absorption Fine Structure (EXAFS) X-ray Absorption Near Edge Structure (XANES)