Non-magnetic ion site disorder effects on the quantum magnetism of a spin-1/2 equilateral triangular lattice antiferromagnet
Non-magnetic ion site disorder effects on the quantum magnetism of a spin-1/2 equilateral triangular lattice antiferromagnet
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DOI：
10.1088/1361-648x/ac5703
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发表时间：
2022-05-18
影响因子：
2.7
通讯作者：
Zhou，H. D.
中科院分区：
文献类型：
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作者：
Huang，Q.;Rawl，R.;Zhou，H. D.
为了研究非磁性离子位无序性对Ba 3 cosb2o9（一种自旋为1/2的等边三角形晶格反铁磁体）量子磁性的影响，我们对Ba 2.87 Sr 0.13 cosb2o9单晶样品进行了直流和交流磁化率、比热、弹性和非弹性中子散射测量。结果表明：Ba 2.87 Sr 0.13 cosb2o9在2.7 K和3.3 K时分别表现出两步磁跃迁；（ii）零场下可能存在120度倾斜自旋结构，有序矩降为1.24 μ B/Co；（iii） H∥ab平面和H∥c轴的一系列自旋态跃迁。对于H∥ab-平面，与上下相相关的磁化平台特征被显著抑制；(4)零场时只有一个间隙模式的非弹性中子散射谱，在9 t时分裂为一个无间隙模式和一个间隙模式。这些特征与母化合物Ba 3 cosb2o9的观察结果明显不同，这表明非磁性离子位无序（Sr掺杂）对磁性能的影响超出了传统预期的交换相互作用的随机性。我们提出了额外的效应，包括量子自旋涨落的增强和通过局部结构扭曲引入可能的空间各向异性。
With the motivation to study how non-magnetic ion site disorder affects the quantum magnetism of Ba 3 CoSb 2 O 9, a spin-1/2 equilateral triangular lattice antiferromagnet, we performed DC and AC susceptibility, specific heat, elastic and inelastic neutron scattering measurements on single crystalline samples of Ba 2.87 Sr 0.13 CoSb 2 O 9 with Sr doping on non-magnetic Ba 2+ ion sites. The results show that Ba 2.87 Sr 0.13 CoSb 2 O 9 exhibits (i) a two-step magnetic transition at 2.7 K and 3.3 K, respectively;(ii) a possible canted 120 degree spin structure at zero field with reduced ordered moment as 1.24 μ B/Co;(iii) a series of spin state transitions for both H∥ ab-plane and H∥ c-axis. For H∥ ab-plane, the magnetization plateau feature related to the up–up–down phase is significantly suppressed;(iv) an inelastic neutron scattering spectrum with only one gapped mode at zero field, which splits to one gapless and one gapped mode at 9 T. All these features are distinctly different from those observed for the parent compound Ba 3 CoSb 2 O 9, which demonstrates that the non-magnetic ion site disorder (the Sr doping) plays a complex role on the magnetic properties beyond the conventionally expected randomization of the exchange interactions. We propose the additional effects including the enhancement of quantum spin fluctuations and introduction of a possible spatial anisotropy through the local structural distortions.