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Electrical resistivity study in heavy-rare-earth A2Ir2O7 iridates

Publication at Faculty of Mathematics and Physics |
2022

Abstract

A2Ir2O7 iridates, where A is a rare earth, crystalize in the ordered pyrochlore structure (space group Fd-3m) for all rare-earth analogues. Both A3+ and Ir4+ ions form sublattices of corner-sharing tetrahedra and are surrounded by 8- and 6- coordinate oxygen cages, respectively.

Many complex (ground) states, e.g., spin ice, spin liquid, or fragmented states stemming from the resulting geometrical frustration have been observed and attracted considerable attention [1]. At higher temperatures, the iridium sublattice tends to order in the so-called all-in-all-out (AIAO) magnetic structure [2] for most analogues, influencing the magnetic moments on the A sublattice at lower temperatures.

A strong spin-orbit coupling tied with the Ir4+ ions was predicted to lead to topological phases such as Weyl semimetal or topological Mott insulator [3,4]. We present a study of electrical transport and magnetic properties of heavy-rare-earth A2Ir2O7 iridates (A=Dy-Lu) synthesized employing the CsCl flux method.

A broad anomaly in the electrical resistivity data connected with the semiconductor-insulator transition is scanned and discussed in comparison to the AIAO ordering of the Ir sublattice [5]. The study is complimented by magnetoresistance measurements and previous magnetic and specific heat results on the same samples.

A comprehensive picture is drawn for this understudied part of the rare-earth A2Ir2O7 series in respect to the connected electrical transport and magnetic properties. [1] E. Lefrançois et al., Nat.

Commun. 8, 209 (2017). [2] H. Jacobsen et al., Phys.

Rev. B 101, 104404 (2020). [3] W.

Witczak-Krempa et al., Annu. Rev.

Condens. Matter Phys. 5, 57-82 (2014). [4] X.

Wan et al., Phys. Rev.

B 83, 205101 (2011). [5] K. Matsuhira et al., J.

Phys. Soc.

Jpn. 80, 094701 (2011).