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arXiv 2108.08893cond-mat.str-el
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非磁性离子位无序对自旋1/2等边三角晶格反铁磁体量子磁性的影响

Non-magnetic ion site disorder effects on the quantum magnetism of a spin-1/2 equilateral triangular lattice antiferromagnet

Q. Huang, R. Rawl, W. W. Xie, E. S. Chou, V. S. Zapf, X. X. Ding, C. Mauws, C. R. Wiebe, E. X. Feng, H. B. Cao, W. Tian, J. Ma, Y. Qiu, N. Butch, H. D. Zhou

摘要:

为了研究非磁性离子位无序对自旋为1/2的等边三角晶格反铁磁体Ba 3CoSb 2 O 9的量子磁性的影响,我们对非磁性离子位Sr掺杂的Ba2.87Sr0.13CoSb2O9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)CoSb_2 O_9分别在2.7 K和3.3 K发生两步磁转变;在零场下可能存在120度倾斜自旋结构,约化有序矩为1.24μB/Co;在H //ab面和H //c轴上均存在一系列自旋态转变。对于H //ab-平面,磁化平台的功能有关的向上向上向下的阶段显着抑制;(iv)非弹性中子散射谱只有一个间隙模式在零场,分裂为一个无间隙和一个有间隙的模式在9 T。所有这些功能是明显不同于所观察到的母体化合物Ba 3CoSb 2 O 9,这表明,非磁性离子位点无序(Sr掺杂)发挥了复杂的作用,超出了传统预期的随机化的交换相互作用的磁性。我们提出的附加效应包括量子自旋涨落的增强和通过局部结构畸变引入可能的空间各向异性。

英文摘要:

With the motivation to study how non-magnetic ion site disorder affects the quantum magnetism of Ba3CoSb2O9, 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 Ba2.87Sr0.13CoSb2O9 with Sr doping on non-magnetic Ba2+ ion sites. The results show that Ba2.87Sr0.13CoSb2O9 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 1.24μB/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 Ba3CoSb2O9, 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.

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