Abstract

The pyrochlore magnet Ce₂Zr₂O₇ has attracted much attention as a quantum spin ice candidate whose novelty derives in part from the dipolar-octupolar nature of the Ce³⁺ pseudospin-1/2 degrees of freedom it possesses. We report heat capacity measurements on single crystal samples of Ce₂Zr₂O₇ down to T~0.1K in a magnetic field along the [$$1,\bar{1},0$$] direction. These measurements show that the broad hump in the zero-field heat capacity moves higher in temperature with increasing field strength and is split into two separate humps by the [$$1,\bar{1},0$$] magnetic field at ~2T. These separate features are due to the decomposition of the pyrochlore lattice into effectively decoupled chains for fields in this direction: One set of chains (α chains) is polarized by the field while the other (β chains) remains free. This situation is similar to that observed in the classical spin ices Ho₂Ti₂O₇ and Dy₂Ti₂O₇, but with the twist that here the strong transverse exchange interactions produce substantial quantum effects. Our theoretical modeling suggests that the β chains are close to a critical state, with nearly-gapless excitations. We also report elastic and inelastic neutron scattering measurements on single crystal Ce₂Zr₂O₇ in [$$1,\bar{1},0$$] and [0,0,1] magnetic fields at temperatures down to T=0.03K. The elastic scattering behaves consistently with the formation of independent chains for a [$$1,\bar{1},0$$] field, while the [0,0,1] field produces a single field-induced elastic magnetic Bragg peak at (0,2,0) and equivalent wavevectors, indicating a polarized spin ice state for fields above ~3T. For both [$$1,\bar{1},0$$] and [0,0,1] magnetic fields, our inelastic neutron scattering results show an approximately dispersionless continuum of scattering that increases in both energy and intensity with increasing field strength. By modeling the complete set of experimental data using numerical linked cluster and semiclassical molecular dynamics calculations, we demonstrate the dominantly multipolar nature of the exchange interactions in Ce₂Zr₂O₇ and the smallness of the parameter θ, which controls the mixing between dipolar and octupolar degrees of freedom. Finally, these results support previous estimates of the microscopic exchange parameters and place strong constraints on the theoretical description of this prominent spin ice candidate.

Authors:

Smith, Evan M.  ^[1];

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Dudemaine, J. ^[2]; Placke, Benedikt Andreas  ^[3];

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Schäfer, Robin  ^[4];

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Yahne, Danielle R. ^[5]; DeLazzer, Tim ^[5]; Fitterman, Avner Menachem ^[2]; Beare, James ^[1]; Gaudet, Jonathan  ^[6];

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Buhariwalla, Connor R. C.  ^[1];

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Podlesnyak, Andrey A.  ^[7];

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Xu, Guangyong ^[8]; Clancy, James P. ^[1]; Movshovich, R. ^[9]; Luke, Graeme M.  ^[1];

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Ross, K. A. ^[10]; Moessner, Roderich ^[3]; Benton, Owen  ^[3];

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Bianchi, Andrea D.  ^[2];

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Gaulin, Bruce D. ^[11]

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+ Show Author Affiliations

1. McMaster Univ., Hamilton, ON (Canada)
2. Univ. of Montreal, QC (Canada); Quebec Network Advanced Materials (RQMP), QC (Canada)
3. Max Planck Society, Dresden (Germany). Max Planck Inst. for the Physics of Complex Systems
4. Max Planck Society, Dresden (Germany). Max Planck Inst. for the Physics of Complex Systems; Boston Univ., MA (United States)
5. Colorado State Univ., Fort Collins, CO (United States)
6. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research; Univ. of Maryland, College Park, MD (United States)
7. Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States)
8. National Inst. of Standards and Technology (NIST), Gaithersburg, MD (United States). Center for Neutron Research
9. Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
10. Colorado State Univ., Fort Collins, CO (United States); Canadian Institute for Advanced Research (CIFAR), Toronto, ON (Canada)
11. McMaster Univ., Hamilton, ON (Canada); Canadian Institute for Advanced Research (CIFAR), Toronto, ON (Canada)

Publication Date:

Mon Aug 28 00:00:00 EDT 2023

Research Org.:

Oak Ridge National Laboratory (ORNL), Oak Ridge, TN (United States). Spallation Neutron Source (SNS)

Sponsoring Org.:

USDOE Office of Science (SC), Basic Energy Sciences (BES); German Research Foundation (DFG); US Air Force Office of Scientific Research (AFOSR)

OSTI Identifier:

1997617

Grant/Contract Number:  

AC05-00OR22725; SFB 1143; FA 9550-20-1-0235

Resource Type:

Accepted Manuscript

Journal Name:

Physical Review. B

Additional Journal Information:

Journal Volume: 108; Journal Issue: 5; Journal ID: ISSN 2469-9950

Publisher:

American Physical Society (APS)

Country of Publication:

United States

Language:

English

Subject:

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; exchange interaction; frustrated magnetism; quantum spin liquid; pyrochlores; cluster expansion; molecular dynamics; neutron scattering; specific heat measurements