Near-ideal molecule-based Haldane spin chain

Journal Article · Mon Jan 27 00:00:00 EST 2020 · Physical Review Research

DOI:https://doi.org/10.1103/PhysRevResearch.2.013082· OSTI ID:1595175

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.

The molecular coordination complex ${\mathrm{NiI}}_2{(3,5-\mathrm{lut})}_4$ [where (3,5-lut) $=$ (3,5-lutidine) $=({\mathrm{C}}_7{\mathrm{H}}_9\mathrm{N}$)] 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– $\mathrm{I}\bullet \bullet \bullet \mathrm{I}$–Ni chains aligned along the $c$ axis. This arrangement leads to an uncommon through-space $\mathrm{I}\bullet \bullet \bullet \mathrm{I}$ magnetic coupling which is directly measured in this work. The net result is a near-ideal realization of the $S=1$ Haldane chain with $J=17.5\mathrm{K}$ and energy gaps of ${\mathrm{\Delta }}^{\parallel }=5.3\mathrm{K}{\mathrm{\Delta }}^{\perp }=7.7\mathrm{K}$, split by the easy-axis single-ion anisotropy $D=-1.2\mathrm{K}$. The ratio $D/J=-0.07$ affords one of the most isotropic Haldane systems yet discovered, while the ratio ${\mathrm{\Delta }}_0/J=0.40\left(1\right)$ (where ${\mathrm{\Delta }}_0$ 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 ${\mu }_0{H}_{\mathrm{c}}^{\parallel }=5.3\mathrm{T}$ and ${\mu }_0{H}_{\mathrm{c}}^{\perp }=4.3\mathrm{T}$, which are readily accessible experimentally and permit investigations across the entirety of the Haldane phase, with the fully polarized state occurring at ${\mu }_0{H}_{\mathrm{s}}^{\parallel }=46.0\mathrm{T}$ and ${\mu }_0{H}_{\mathrm{s}}^{\perp }=50.7\mathrm{T}$. 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 $20\mathrm{mK}$ and emergent end-chain effects are observed in the gapped state, as evidenced by detailed low-temperature measurements.

• Research Organization: Los Alamos National Laboratory (LANL), Los Alamos, NM (United States)
• Sponsoring Organization: USDOE Office of Science (SC), Basic Energy Sciences (BES); European Research Council (ERC); National Science Foundation (NSF); Engineering and Physical Sciences Research Council (EPSRC)
• Grant/Contract Number: AC02-06CH11357; 89233218CNA000001; DMR-1157490; DMR-1703003; CHE-1834750; EP/N023803/1; EP/N024028/1; EP/N032128/1
• OSTI ID: 1595175
• Alternate ID(s): OSTI ID: 1783522
• Report Number(s): LA-UR-19-27659; PPRHAI; 013082
• Journal Information: Physical Review Research, Journal Name: Physical Review Research Vol. 2 Journal Issue: 1; ISSN 2643-1564
• Publisher: American Physical Society
• Country of Publication: United States
• Language: English

Related Subjects

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY
High magnetic field science
quantum phase transitions
topological phases of matter
1-dimensional spin chains