Tl2Ir2O7: A Pauli Paramagnetic Metal, Proximal to a Metal Insulator Transition

Hai L. Feng, Chang Jong Kang, Zheng Deng, Mark Croft, Sizhan Liu, Trevor A. Tyson, Saul H. Lapidus, Corey E. Frank, Youguo Shi, Changqing Jin, David Walker, Gabriel Kotliar, Martha Greenblatt

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A polycrystalline sample of Tl2Ir2O7 was synthesized by high-pressure and high-temperature methods. Tl2Ir2O7 crystallizes in the cubic pyrochlore structure with space group Fd3¯ m (No. 227). The Ir4+ oxidation state is confirmed by Ir-L3 X-ray absorption near-edge spectroscopy. Combined temperature-dependent magnetic susceptibility, resistivity, specific heat, and DFT+DMFT calculation data show that Tl2Ir2O7 is a Pauli paramagnetic metal, but it is close to a metal-insulator transition. The effective ionic size of Tl3+ is much smaller than that of Pr3+ in metallic Pr2Ir2O7; hence, Tl2Ir2O7 would be expected to be insulating according to the established phase diagram of the pyrochlore iridate compounds, A3+2Ir4+2O7. Our experimental and theoretical studies indicate that Tl2Ir2O7 is uniquely different from the current A3+2Ir4+2O7 phase diagram. This uniqueness is attributed primarily to the electronic configuration difference between Tl3+ and rare-earth ions, which plays a substantial role in determining the Ir-O-Ir bond angle, and the corresponding electrical and magnetic properties.

Original languageEnglish (US)
Pages (from-to)4424-4433
Number of pages10
JournalInorganic Chemistry
Issue number7
StatePublished - Apr 5 2021

All Science Journal Classification (ASJC) codes

  • Physical and Theoretical Chemistry
  • Inorganic Chemistry


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