Abstract
Motivated by the variation in reported lattice parameters of floating-zone-grown Nd2Zr2O7 crystals, we have performed a detailed study of the relationship between synthesis environment, structural disorder, and magnetic properties. Using a combination of polycrystalline standards, electron-probe microanalysis, and scattering techniques, we show that crystals grown under atmospheric conditions have a reduced lattice parameter relative to pristine polycrystalline powders due to occupation of the Nd site by excess Zr (i.e., negative stuffing). In contrast, crystals grown under high-pressure Ar are nearly stoichiometric with an average lattice parameter approaching the polycrystalline value. While minimal disorder of the oxygen sublattices is observed on the scale of the average structure, neutron pair-distribution function analysis indicates a highly local disorder of the oxygen coordination, which is only weakly dependent on growth environment. Most importantly, our magnetization, heat capacity, and single-crystal neutron scattering data show that the magnetic properties of crystals grown under high-pressure Ar match closely with those of stoichiometric powders. Neutron scattering measurements reveal that the signature of magnetic moment fragmentation - the coexistence of all-in-all-out (AIAO) magnetic Bragg peaks and diffuse pinch-point scattering due to spin-ice correlations-persists in these nearly stoichiometric crystals. However, in addition to an increased AIAO transition temperature, the diffuse signal is seemingly stabilized and remains nearly unchanged upon warming to 800 mK. This behavior indicates that both the AIAO magnetic order and spin-ice correlations are sensitive to deviations of the Nd stoichiometry.
| Original language | English |
|---|---|
| Article number | 084403 |
| Journal | Physical Review Materials |
| Volume | 5 |
| Issue number | 8 |
| DOIs | |
| State | Published - Aug 2021 |
Funding
We would like to thank Carlos Levi for a number of insightful discussions. This work was partially supported by the U.S. Department of Energy, Office of Basic Energy Sciences, Division of Materials Sciences and Engineering under Award No. DE-SC0017752. A portion of this research used resources at the Spallation Neutron Source, a DOE Office of Science User Facility operated by the Oak Ridge National Laboratory. Use of the Advanced Photon Source at Argonne National Laboratory was supported by the U. S. Department of Energy, Office of Science, Office of Basic Energy Sciences, under Contract No. DE-AC02-06CH11357. This work made use of the MRL Shared Experimental Facilities which are supported by the MRSEC Program of the NSF under Award No. DMR 1720256, a member of the NSF-funded Materials Research Facilities Network, and it also used facilities supported via the UC Santa Barbara NSF Quantum Foundry funded via the Q-AMASE-i program under Award No. DMR-1906325. This work was also supported by the Office of Naval Research under Grant No. N00014-19-1-2377 monitored by Dr. D.A. Shifler. Additional funding support for crystal growth was provided by the W. M. Keck Foundation. G.L. gratefully acknowledges support for this work from the National Science Foundation (NSF) through DMR 1904980 with additional support provided by Bates College internal funding. The identification of any commercial product or trade name does not imply endorsement or recommendation by the National Institute of Standards and Technology.
| Funders | Funder number |
|---|---|
| NSF-funded | |
| UC Santa Barbara NSF | DMR-1906325 |
| National Science Foundation | DMR 1904980 |
| Office of Naval Research | N00014-19-1-2377 |
| U.S. Department of Energy | |
| National Institute of Standards and Technology | |
| W. M. Keck Foundation | |
| Office of Science | DE-AC02-06CH11357 |
| Basic Energy Sciences | |
| Oak Ridge National Laboratory | |
| Division of Materials Sciences and Engineering | DE-SC0017752 |
| Materials Research Science and Engineering Center, Harvard University | DMR 1720256 |
| Bates College |