Intermediate field-induced phase of the honeycomb magnet BaCo$_2$(AsO$_4$)$_2$
Prashanta K. Mukharjee, Bin Shen, Sebastian Erdmann, Anton Jesche, Julian Kaiser, Priya R. Baral, Oksana Zaharko, Philipp Gegenwart, Alexander A. Tsirlin
本文通过磁化、量热、膨胀测量和中子衍射研究 BaCo$_2$(AsO$_4$)$_2$ 的相图，发现 0.51–0.55 T 的中间相仍存在磁布拉格峰，排除自旋液体性质，并揭示晶格效应的重要作用。
摘要：
我们利用磁化测量、量热法、高分辨率电容膨胀测量以及单晶中子衍射，探索了各向异性蜂窝磁体 BaCo$_2$(AsO$_4$)$_2$ 的温度-磁场相图。我们的数据揭示了面内磁场下观察到的四种不同的有序态。特别令人感兴趣的是介于 0.51 至 0.55 T 之间的狭窄区域，该区域将上-上-下序与完全极化态分隔开，并与已报道的自旋液体行为特征出现的场范围重合。我们表明，磁布拉格峰在该中间相中持续存在，从而排除了其自旋液体性质。然而，核布拉格峰同时出现的非单调演化表明晶格参与其中，这在相图的其他区域中也有体现，即进入磁有序态时观察到样品长度发生显著变化。我们的数据强调了晶格效应在 BaCo$_2$(AsO$_4$)$_2$ 中的重要性。
英文摘要：
We use magnetometry, calorimetry, and high-resolution capacitive dilatometry, as well as single-crystal neutron diffraction to explore temperature-field phase diagram of the anisotropic honeycomb magnet BaCo$_2$(AsO$_4)_2$. Our data reveal four distinct ordered states observed for in-plane magnetic fields. Of particular interest is the narrow region between 0.51 and 0.55 T that separates the up-up-down order from the fully polarized state and coincides with the field range where signatures of the spin-liquid behavior have been reported. We show that magnetic Bragg peaks persist in this intermediate phase, thus ruling out its spin-liquid nature. However, the simultaneous nonmonotonic evolution of nuclear Bragg peaks suggests the involvement of the lattice, witnessed also in other regions of the phase diagram where large changes in the sample length are observed upon entering the magnetically ordered states. Our data highlight the importance of lattice effects in BaCo$_2$(AsO$_4)_2$.
Ab initio guided minimal model for the "Kitaev" material BaCo$_2$(AsO$_4$)$_2$: Importance of direct hopping, third-neighbor exchange and quantum fluctuations
Mechanism of Incommensurate Magnetic Order in $\mathrm{BaCo_2(AsO_4)_2}$: Interplay of Frustrated Further-Neighbor Exchanges and Bond-Directional Anisotropy
Qom University of Technology（库姆理工大学）；University of Toronto（多伦多大学）；Shahrekord University（沙赫里克尔德大学）
Field-induced first order transitions and phase coexistence in the Kitaev quantum spin liquid candidate BaCo2(AsO4)2
Rice University（赖斯大学）；Department of Physics and Astronomy, Rice University（赖斯大学物理与天文学系）；Rice Laboratory for Emergent Magnetic Materials and Smalley-Curl Institute, Rice University（赖斯大学涌现磁性材料实验室及Smalley-Curl研究所）；Department of Physics and Center for Quantum Frontiers of Research & Technology (QFort), National Cheng Kung University（国立成功大学物理系及量子前沿研究与技术中心）；Department of Physics, Boston College（波士顿学院物理系）；Australian Nuclear Science and Technology Organization (ANSTO)（澳大利亚核科学与技术组织）
Comparative Raman Scattering Study of Crystal Field Excitations in Co-based Quantum Magnets
Wake Forest University（维克森林大学）；Johns Hopkins University（约翰斯·霍普金斯大学）；National High Magnetic Field Laboratory（国家高磁场实验室）；Princeton University（普林斯顿大学）；University of Tennessee, Knoxville（田纳西大学诺克斯维尔分校）；Georgia Institute of Technology（佐治亚理工学院）
