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

Document Type

Article

Publication Date

4-5-2021

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.

Identifier

85103461246 (Scopus)

Publication Title

Inorganic Chemistry

External Full Text Location

https://doi.org/10.1021/acs.inorgchem.0c03124

e-ISSN

1520510X

ISSN

00201669

PubMed ID

33705141

First Page

4424

Last Page

4433

Issue

7

Volume

60

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