Combining microscopic and macroscopic probes to untangle the single-ion anisotropy and exchange energies in an S=1 quantum antiferromagnet

Jamie Brambleby, Jamie L. Manson, Paul A. Goddard, Matthew B. Stone, Roger D. Johnson, Pascal Manuel, Jacqueline A. Villa, Craig M. Brown, Helen Lu, Shalinee Chikara, Vivien Zapf, Saul H. Lapidus, Rebecca Scatena, Piero Macchi, Yu Sheng Chen, Lai Chin Wu, John Singleton

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    21 Scopus citations

    Abstract

    The magnetic ground state of the quasi-one-dimensional spin-1 antiferromagnetic chain is sensitive to the relative sizes of the single-ion anisotropy (D) and the intrachain (J) and interchain (J′) exchange interactions. The ratios D/J and J′/J dictate the material's placement in one of three competing phases: a Haldane gapped phase, a quantum paramagnet, and an XY-ordered state, with a quantum critical point at their junction. We have identified [Ni(HF2)(pyz)2]SbF6, where pyz = pyrazine, as a rare candidate in which this behavior can be explored in detail. Combining neutron scattering (elastic and inelastic) in applied magnetic fields of up to 10 tesla and magnetization measurements in fields of up to 60 tesla with numerical modeling of experimental observables, we are able to obtain accurate values of all of the parameters of the Hamiltonian [D=13.3(1) K, J=10.4(3) K, and J′=1.4(2) K], despite the polycrystalline nature of the sample. Density-functional theory calculations result in similar couplings (J=9.2 K, J′=1.8 K) and predict that the majority of the total spin population resides on the Ni(II) ion, while the remaining spin density is delocalized over both ligand types. The general procedures outlined in this paper permit phase boundaries and quantum-critical points to be explored in anisotropic systems for which single crystals are as yet unavailable.

    Original languageEnglish
    Article number134435
    JournalPhysical Review B
    Volume95
    Issue number13
    DOIs
    StatePublished - Apr 20 2017

    Funding

    The work at EWU was supported by the National Science Foundation (NSF) under Grant No. DMR-1306158 and by the National Institute of Standards and Technology (NIST) Cooperative Agreement 70NANB15H262. ChemMatCARS Sector 15 is principally supported by the Divisions of Chemistry (CHE), NSF, under Grant No. CHE-1346572. Use of the Advanced Photon Source, an Office of Science User Facility operated for the U.S. Department of Energy (DoE) Office of Science by Argonne National Laboratory, was supported by the U.S. DoE under Contract No. DE-AC02-06CH11357. We acknowledge the support of NIST, U.S. Department of Commerce (DoC), in providing their neutron research facilities used in this work; identification of any commercial product or trade name does not imply endorsement or recommendation by NIST. Work performed at the National High Magnetic Field Laboratory, USA, was supported by NSF Cooperative Agreement DMR-1157490, the State of Florida, U.S. DoE, and through the DoE Basic Energy Science Field Work Project Science in 100 T. M.B.S. was supported by the Scientific User Facilities Division, Office of Basic Energy Sciences, U.S. Department of Energy. We gratefully acknowledge the ISIS-RAL facility for the provision of beamtime. J.B. thanks EPSRC for financial support. P.A.G. acknowledges that this project has received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation programme (Grant agreement No. 681260). Research at the University of Bern was funded by the Swiss NSF (project 160157). J.S. acknowledges a Visiting Professorship from the University of Oxford that enabled some of the experiments reported in this paper.

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