Wallace M K, LaBarre P G, Li Jun, Pi S-T, Pickett W E, Dessau D S, Haskel D, Ramirez A P, Subramanian M A
Department of Chemistry, Oregon State University, Corvallis, OR, 97331, USA.
Department of Physics, University of California Santa Cruz, Santa Cruz, CA, 95064, USA.
Sci Rep. 2018 Apr 26;8(1):6605. doi: 10.1038/s41598-018-25028-0.
Compounds with honeycomb structures occupied by strong spin orbit coupled (SOC) moments are considered to be candidate Kitaev quantum spin liquids. Here we present the first example of Os on a honeycomb structure, LiOsO (C2/c, a = 5.09 Å, b = 8.81 Å, c = 9.83 Å, β = 99.3°). Neutron diffraction shows large site disorder in the honeycomb layer and X-ray absorption spectroscopy indicates a valence state of Os (4.7 ± 0.2), consistent with the nominal concentration. We observe a transport band gap of Δ = 243 ± 23 meV, a large van Vleck susceptibility, and an effective moment of 0.85 μ, much lower than expected from 70% Os(+5). No evidence of long range order is found above 0.10 K but a spin glass-like peak in ac-susceptibility is observed at 0.5 K. The specific heat displays an impurity spin contribution in addition to a power law ∝T. Applied density functional theory (DFT) leads to a reduced moment, suggesting incipient itineracy of the valence electrons, and finding evidence that Li over stoichiometry leads to Os(4+)-Os(5+) mixed valence. This local picture is discussed in light of the site disorder and a possible underlying quantum spin liquid state.
具有由强自旋轨道耦合（SOC）矩占据的蜂窝结构的化合物被认为是候选的基塔耶夫量子自旋液体。在这里，我们展示了蜂窝结构上Os的首个例子，即LiOsO（C2/c，a = 5.09 Å，b = 8.81 Å，c = 9.83 Å，β = 99.3°）。中子衍射表明蜂窝层中存在较大的位点无序，X射线吸收光谱表明Os的价态为（4.7±0.2），与标称浓度一致。我们观察到一个传输带隙Δ = 243±23 meV，一个大的范弗莱克磁化率，以及一个有效磁矩为0.85 μ，远低于70% Os(+5)所预期的值。在0.10 K以上未发现长程序的证据，但在0.5 K时观察到交流磁化率中有一个类似自旋玻璃的峰。比热除了呈现幂律∝T外，还显示出杂质自旋贡献。应用密度泛函理论（DFT）导致磁矩减小，表明价电子开始具有巡游性，并发现有证据表明锂的化学计量过量导致了Os(4+)-Os(5+)混合价态。根据位点无序和可能的潜在量子自旋液体状态对这种局域情况进行了讨论。
