Iridate Li8IrO6: An Antiferromagnetic Insulator

Callista M Skaggs; Peter E Siegfried; Chang-Jong Kang; Craig M Brown; Fu Chen; Lu Ma; Steven N Ehrlich; Yan Xin; Mark Croft; Wenqian Xu; Saul H Lapidus; Nirmal J Ghimire; Xiaoyan Tan

doi:10.1021/acs.inorgchem.1c02535

Iridate Li₈IrO₆: An Antiferromagnetic Insulator

Inorg Chem. 2021 Nov 15;60(22):17201-17211. doi: 10.1021/acs.inorgchem.1c02535. Epub 2021 Nov 4.

Authors

Callista M Skaggs¹, Peter E Siegfried^{2

3}, Chang-Jong Kang⁴, Craig M Brown⁵, Fu Chen⁶, Lu Ma⁷, Steven N Ehrlich⁷, Yan Xin⁸, Mark Croft⁹, Wenqian Xu¹⁰, Saul H Lapidus¹⁰, Nirmal J Ghimire^{2

3}, Xiaoyan Tan¹

Affiliations

¹ Department of Chemistry and Biochemistry, George Mason University, Fairfax, Virginia 22030, United States.
² Department of Physics and Astronomy, George Mason University, Fairfax, Virginia 22030, United States.
³ Quantum Science and Engineering Center, George Mason University, Fairfax, Virginia 22030, United States.
⁴ Department of Physics, Chungnam National University, Daejeon 34134, Republic of Korea.
⁵ National Institute of Standards and Technology, Gaithersburg, Maryland 20899, United States.
⁶ Department of Chemistry and Biochemistry, University of Maryland, College Park, Maryland 20742, United States.
⁷ NSLS-II, Brookhaven National Laboratory, Upton, New York 11973, United States.
⁸ National High Magnetic Field Laboratory, Tallahassee, Florida 32310, United States.
⁹ Department of Physics and Astronomy, Rutgers, The State University of New Jersey, Piscataway, New Jersey 08854, United States.
¹⁰ X-ray Science Division, Advanced Photon Source, Argonne National Laboratory, Lemont, Illinois 60439, United States.

PMID: 34735136
DOI: 10.1021/acs.inorgchem.1c02535

Abstract

A polycrystalline iridate Li₈IrO₆ material was prepared via heating Li₂O and IrO₂ starting materials in a sealed quartz tube at 650 °C for 48 h. The structure was determined from Rietveld refinement of room-temperature powder neutron diffraction data. Li₈IrO₆ adopts the nonpolar space group R3̅ with Li atoms occupying the tetrahedral and octahedral sites, which is supported by the electron diffraction and solid-state ⁷Li NMR. This results in a crystal structure consisting of LiO₄ tetrahedral layers alternating with mixed IrO₆ and LiO₆ octahedral layers along the crystallographic c-axis. The +4 oxidation state of Ir⁴⁺ was confirmed by near-edge X-ray absorption spectroscopy. An in situ synchrotron X-ray diffraction study of Li₈IrO₆ indicates that the sample is stable up to 1000 °C and exhibits no structural transitions. Magnetic measurements suggest long-range antiferromagnetic ordering with a Néel temperature (T_N) of 4 K, which is corroborated by heat capacity measurements. The localized effective moment μ_eff (Ir) = 1.73 μ_B and insulating character indicate that Li₈IrO₆ is a correlated insulator. First-principles calculations support the nonpolar crystal structure and reveal the insulating behavior both in paramagnetic and antiferromagnetic states.