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Near-ideal molecule-based Haldane spin chain.

Williams, Robert C. and Blackmore, William J. A. and Curley, Samuel P. M. and Lees, Martin R. and Birnbaum, Serena M. and Singleton, John and Huddart, Benjamin M. and Hicken, Thomas J. and Lancaster, Tom and Blundell, Stephen J. and Xiao, Fan and Ozarowski, Andrew and Pratt, Francis L. and Voneshen, David J. and Guguchia, Zurab and Baines, Christopher and Schlueter, John A. and Villa, Danielle Y. and Manson, Jamie L. and Goddard, Paul A. (2020) 'Near-ideal molecule-based Haldane spin chain.', Physical review research., 2 (1). 013082 .

Abstract

The molecular coordination complex NiI2 (3, 5-lut)4 [where (3,5-lut) = (3,5-lutidine) = (C7H9N)] has been synthesized and characterized by several techniques including synchrotron x-ray diffraction, electron-spin resonance, superconducting quantum interference device magnetometry, pulsed-field magnetization, inelastic neutron scattering, and muon spin relaxation. Templated by the configuration of 3,5-lut ligands the molecules pack in-registry with the Ni–I ··· I–Ni chains aligned along the c axis. This arrangement leads to an uncommon through-space I ··· I magnetic coupling which is directly measured in this work. The net result is a near-ideal realization of the S = 1 Haldane chain with J = 17.5 K and energy gaps of = 5.3 K ⊥ = 7.7 K, split by the easy-axis single-ion anisotropy D = −1.2 K. The ratio D/J = −0.07 affords one of the most isotropic Haldane systems yet discovered, while the ratio 0/J = 0.40(1) (where 0 is the average gap size) is close to its ideal theoretical value, suggesting a very high degree of magnetic isolation of the spin chains in this material. The Haldane gap is closed by orientation-dependent critical fields μ0H c = 5.3 T and μ0H⊥ c = 4.3 T, which are readily accessible experimentally and permit investigations across the entirety of the Haldane phase, with the fully polarized state occurring at μ0H s = 46.0 T and μ0H⊥ s = 50.7 T. The results are explicable within the so-called fermion model, in contrast to other reported easy-axis Haldane systems. Zero-field magnetic order is absent down to 20 mK and emergent end-chain effects are observed in the gapped state, as evidenced by detailed low-temperature measurements.

Item Type:Article
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Status:Peer-reviewed
Publisher Web site:https://doi.org/10.1103/PhysRevResearch.2.013082
Publisher statement:Published by the American Physical Society under the terms of the Creative Commons Attribution 4.0 International license. Further distribution of this work must maintain attribution to the author(s) and the published article's title, journal citation, and DOI.
Date accepted:No date available
Date deposited:29 January 2020
Date of first online publication:27 January 2020
Date first made open access:29 January 2020

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