Yuan Fang, Cronkwright Zachery W, Lussier Joey A, Wiebe Christopher R, Dube Paul A, Thompson Corey M, Munsie Timothy J S, Luke Graeme M, Greedan John E
Brockhouse Institute for Materials Research, McMaster University, Hamilton, Ontario L8S 4L8, Canada.
Department of Chemistry, University of Winnipeg, Winnipeg, R3B 2E9 Manitoba, Canada.
Inorg Chem. 2021 Nov 1;60(21):16652-16657. doi: 10.1021/acs.inorgchem.1c02521. Epub 2021 Oct 19.
The synthesis and characterization of the double perovskite SrLaLiOsO is presented. It is isostructural (2/) and isoelectronic (5d) with SrLaMgReO, which has been reported previously. The cell volumes are the same to within 1.4%: i.e., these perovskites are doppelgängers. In a previous study SrLaMgReO showed no sign of spin order to 2 K. New data at lower temperatures disclose a maximum in the dc susceptibility near 1.5 K. As the Curie-Weiss (C-W) temperature (Θ) for this material is -161 K, an enormous frustration index, ≈ 100, is implied ( = |Θ|/). On the other hand, SrLaLiOsO does not follow the C-W law over the investigated susceptibility range, 2-300 K. Fitting with an added temperature independent term (TIP) gives μ = 1.96 μ, Θ = -102 K, and TIP = 1.01 × 10 emu/mol. A clear zero-field-cooled (ZFC), field-cooled (FC) divergence in the dc data occurs at ∼10 K, suggesting a much reduced frustration index, ≈ 10, relative to SrLaMgReO. The real part of the ac susceptibility data, χ', shows a frequency shift that is consistent with a spin glass ground state according to the Mydosh criterion. Heat capacity data for SrLaLiOsO show no sign of a λ peak at 10 K and a linear dependence on temperature below 10 K, also supporting a spin glass ground state. A spin frozen ground state for SrLaMgReO could not be established from χ' data due to a much weaker signal. Nonetheless, the 10-fold difference in between these doppelgänger materials is remarkable. It is possible that the enhanced covalency with the oxide ligands for Os relative to Re plays a major role here. Finally, a comparison with isostructural LaLiReO (with a much smaller ≈ 4) is made and a correlation between the frustration level and the sense of the local distortion of the Re(Os)-O octahedron is pointed out.
本文介绍了双钙钛矿SrLaLiOsO的合成与表征。它与之前报道的SrLaMgReO具有相同的结构（2/）和等电子体（5d）。晶胞体积相差在1.4%以内，即这些钙钛矿是相似物。在之前的一项研究中，SrLaMgReO在2 K时未显示出自旋有序的迹象。低温下的新数据揭示了在1.5 K附近直流磁化率出现最大值。由于该材料的居里-外斯（C-W）温度（Θ）为-161 K，这意味着一个巨大的失配指数，约为100（ = |Θ|/）。另一方面，在2 - 300 K的研究磁化率范围内，SrLaLiOsO不遵循C-W定律。添加一个与温度无关的项（TIP）进行拟合，得到μ = 1.96 μ，Θ = -102 K，TIP = 1.01 × 10 emu/mol。直流数据中明显的零场冷却（ZFC）、场冷却（FC）发散出现在约10 K处，这表明相对于SrLaMgReO，失配指数大大降低，约为10。根据米多什准则，交流磁化率数据的实部χ'显示出与自旋玻璃基态一致的频率偏移。SrLaLiOsO的热容数据在10 K处没有λ峰的迹象，并且在10 K以下与温度呈线性关系，这也支持了自旋玻璃基态。由于信号弱得多，无法从χ'数据确定SrLaMgReO的自旋冻结基态。尽管如此，这些相似材料之间的失配指数相差10倍是很显著的。相对于Re，Os与氧化物配体增强的共价性可能在这里起主要作用。最后，与结构相同的LaLiReO（失配指数小得多，约为4）进行了比较，并指出了失配程度与Re(Os)-O八面体局部畸变方向之间的相关性。
