Near-ideal molecule-based Haldane spin chain

Williams, Robert C.; Blackmore, William J.A.; Curley, Samuel P.M.; Lees, Martin R.; Birnbaum, Serena M.; Singleton, John; Huddart, Benjamin M.; Hicken, Thomas J.; Lancaster, Tom; Blundell, Stephen J.; Xiao, Fan; Ozarowski, Andrew; Pratt, Francis L.; Voneshen, David J.; Guguchia, Zurab; Baines, Christopher; Schlueter, John A.; Villa, Danielle Y.; Manson, Jamie L.; Goddard, Paul A.

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.

Citation

Williams, R. C., Blackmore, W. J., Curley, S. P., Lees, M. R., Birnbaum, S. M., Singleton, J., Huddart, B. M., Hicken, T. J., Lancaster, T., Blundell, S. J., Xiao, F., Ozarowski, A., Pratt, F. L., Voneshen, D. J., Guguchia, Z., Baines, C., Schlueter, J. A., Villa, D. Y., Manson, J. L., & Goddard, P. A. (2020). Near-ideal molecule-based Haldane spin chain. Physical Review Research, 2(1), Article 013082. https://doi.org/10.1103/physrevresearch.2.013082

• Journal Article Type: Article
• Online Publication Date: Jan 27, 2020
• Publication Date: Jan 31, 2020
• Deposit Date: Jan 29, 2020
• Publicly Available Date: Jan 29, 2020
• Journal: Physical Review Research
• Publisher: American Physical Society
• Peer Reviewed: Peer Reviewed
• Volume: 2
• Issue: 1
• Article Number: 013082
• DOI: https://doi.org/10.1103/physrevresearch.2.013082
• Public URL: https://durham-repository.worktribe.com/output/1309283