A Near-Ideal Molecule-Based Haldane Spin-Chain
| Autor: | 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. |
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| Rok vydání: | 2019 |
| Předmět: | |
| Zdroj: | Phys. Rev. Research 2, 013082 (2020) |
| Druh dokumentu: | Working Paper |
| DOI: | 10.1103/PhysRevResearch.2.013082 |
| Popis: | The molecular coordination complex NiI$_2$(3,5-lut)$_4$ [where (3,5-lut) $=$ (3,5-lutidine) $=$ (C$_7$H$_9$N)] has been synthesized and characterized by several techniques including synchrotron X-ray diffraction, ESR, SQUID 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$\cdots$I--Ni chains aligned along the $c$--axis. This arrangement leads to through-space I$\cdots$I magnetic coupling which is directly measured for the first time in this work. The net result is a near-ideal realization of the $S = 1$ Haldane chain with $J = 17.5~\rm{K}$ and energy gaps of $\Delta^{\parallel} = 5.3~{\rm K}$ $\Delta^{\perp} =7.7~{\rm K}$, split by the easy-axis single-ion anisotropy $D=-1.2~{\rm K}$. The ratio $D/J = -0.07$ affords one of the most isotropic Haldane systems yet discovered, while the ratio $\Delta_0/J = 0.40(1)$ (where $\Delta_0$ 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 $\mu_0H_{\rm c}^{\parallel} = 5.3~\rm{T}$ and $\mu_0H_{\rm c}^{\perp} = 4.3~\rm{T}$, which are readily accessible experimentally and permit investigations across the entirety of the Haldane phase, with the fully polarized state occurring at $\mu_0 H_{\rm s}^{\parallel}=46.0~\rm{T}$ and $\mu_0 H_{\rm s}^{\perp}=50.7~\rm{T}$. 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 $20~{\rm mK}$ and emergent end-chain effects are observed in the gapped state, as evidenced by detailed low-temperature measurements. Comment: 13 pages, 8 figures plus supporting information |
| Databáze: | arXiv |
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