Global Metal-Insulator Transition in the Pyrochlore Iridates (Nd<sub>1-x</sub>Ca<sub>x</sub>)<sub>2</sub>Ir<sub>2</sub>O<sub>7</sub>

ORAL

Abstract

We report on the suppression of the metal-insulator transition (MIT) in polycrystalline samples of Nd2Ir2O7 under substitution of Nd for Ca. Each calcium ion effectively dopes one hole on an Ir4+ (5d4, jeff=1/2) site, mediating a filling-controlled Mott-like transition. Ca substitution also changes bandwidth by modulating Ir-O bond lengths and angles, without altering site symmetry. Local structure and absorption spectroscopy confirm that Ca substitution does not result in phase separation or large changes to Ir electronic configuration. The MIT has a coincident antiferromagnetic transition on the Ir sublattice (TN = TMIT) for all measured samples, which both decrease with Ca content. Weak low-temperature upturns in susceptibility and resistivity for samples with high Ca content suggest that Nd sublattice magnetism couples to carriers in the metallic regime.

*This work was supported primarily by ARO Award No. W911NF-16-1-0361. The MRL Shared Experimental Facilities are supported by the MRSEC Program of the NSF under Award No. DMR 1720256, a member of the NSF-funded Materials Research Facilities Network. Research at CHESS is supported by the NSF under Award No. DMR-1332208. Use of the APS at ANL was supported by the U.S. DOE Office of Science under Contract DE-AC02-06CH11357.

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Presenters

  • Zach Porter

    • Materials, University of California, Santa Barbara
    • University of California, Santa Barbara

Authors

  • Zach Porter

    • Materials, University of California, Santa Barbara
    • University of California, Santa Barbara

  • Eli Zoghlin

    • University of California, Santa Barbara
    • Materials Department, University of California, Santa Barbara
    • Materials, University of California, Santa Barbara

  • Geneva Laurita

    • Chemistry and Biochemistry, Bates College
    • Bates College

  • Jacob P.C. Ruff

    • Advanced Photon Source, Argonne National Laboratory
    • CHESS

  • Yongseong Choi

    • Argonne National Laboratory
    • Advanced Photon Source, Argonne National Laboratory
    • Advanced Photon Source
    • Argonne National Lab

  • Daniel Haskel

    • Advanced Photon Source, Argonne National Laboratory
    • Advanced Photon Source
    • Argonne National Lab

  • Stephen Wilson

    • University of California, Santa Barbara
    • Materials Department, University of California, Santa Barbara
    • Materials, University of California Santa Barbara
    • Materials, University of California, Santa Barbara
    • UC Santa Barbara