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

doi:10.1021/acs.inorgchem.0c03124

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

Physics

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6 Scopus citations

Abstract

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 language	English (US)
Pages (from-to)	4424-4433
Number of pages	10
Journal	Inorganic Chemistry
Volume	60
Issue number	7
DOIs	https://doi.org/10.1021/acs.inorgchem.0c03124
State	Published - Apr 5 2021

All Science Journal Classification (ASJC) codes

Physical and Theoretical Chemistry
Inorganic Chemistry

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10.1021/acs.inorgchem.0c03124

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

abstract = "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.",

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

note = "Publisher Copyright: {\textcopyright} 2021 American Chemical Society.",

year = "2021",

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doi = "10.1021/acs.inorgchem.0c03124",

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T1 - Tl2Ir2O7

T2 - A Pauli Paramagnetic Metal, Proximal to a Metal Insulator Transition

AU - Feng, Hai L.

AU - Kang, Chang Jong

AU - Deng, Zheng

AU - Croft, Mark

AU - Liu, Sizhan

AU - Tyson, Trevor A.

AU - Lapidus, Saul H.

AU - Frank, Corey E.

AU - Shi, Youguo

AU - Jin, Changqing

AU - Walker, David

AU - Kotliar, Gabriel

AU - Greenblatt, Martha

PY - 2021/4/5

Y1 - 2021/4/5

N2 - 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.

AB - 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.

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

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