Spin-polarized scanning tunneling microscopy (SPSTM) was used to directly image nanoscale Néel skyrmions in a SrIrO3 / SrRuO3 bilayer system that are among the smallest reported to date in any system. Off-axis magnetron sputtering was used to cap epitaxial films of the oxide ferromagnet SRO with 2 unit cells of SrIrO3, intended to provide interfacial spin orbit coupling. Atomic resolution STM imaging and tunneling spectroscopy were used to identify island-like SrIrO3 grains and small regions of bare SrRuO3. Isolated skyrmions were only observed in SrIrO3-covered regions of the film, and exhibited a distribution of sizes and shapes with an average diameter of 3 nm. We found that skyrmions must be fully contained within, but may be smaller than, any given SrIrO3 region. Additionally, skyrmions were observed on SrIrO3 islands of varying thickness without loss of SPSTM contrast, suggesting the magnetic texture lies within the SrIrO3 island rather than the underlying ferromagnetic SrRuO3. Density functional theory calculations suggest this could be due to a small induced magnetic moment associated with IrO layers in the SrIrO3 film.
Spin-polarized scanning tunneling microscopy characteristics of skyrmionic spin structures exhibiting various topologies
拓扑磁性物体的正确识别是实验中的一个重要问题。利用自旋极化扫描隧道显微镜（SP-STM）计算方法，研究了（Pt $_{1-x}$ Ir $_{x}$）Fe/Pd（111）双金属磁性薄膜中具有不同拓扑电荷（$Q=-3,-2,-1,0,+1,+2$）的亚稳Skyrmionic自旋结构.我们发现，一个平面外磁化尖端已经导致在不同的skyrmionic结构对应于它们的对称性在区别SP-STM对比。我们的工作还建立了一个了解的平面内SP-STM对比度和skyrmionic拓扑结构之间的关系，通过调查的平面内的角度之间的变化的自旋沿周边的结构，其特征在于局部涡度或线密度的缠绕数。对于自旋结构表现出一个统一的符号的局部涡度在整个skyrmionic区域，我们证明，（i）$|Q|$可以确定从一个单一的SP-STM图像所采取的任何面内磁化尖端，和（ii）面内尖端磁化旋转提供的符号$Q$独立的有效自旋极化在隧道结中的符号。我们还讨论了局部涡度改变符号的情况。最后，通过增加铱含量的PtIr覆盖层，我们发现一个出现次级外环面内SP-STM的对比度，这是有吸引力的skyrmions或antiskyrmions的指示。
Atomic-Scale Surface Imaging of bulk Epitaxial CsPbBr3 Perovskite Single Crystals on Mica using Light Assisted Scanning Tunneling Microscopy at Low-Temperature (80 K)
Institut FEMTO-ST, Univ. Marie et Louis Pasteur, CNRS（FEMTO-ST研究所，玛丽和路易·巴斯德大学，法国国家科学研究中心）；Department of Physics and Astronomy, Rutgers, the State University of New Jersey（物理与天文学系，新泽西州立罗格斯大学）；Institut des Sciences Moléculaires d’Orsay (ISMO), CNRS, Univ. Paris Sud, Université Paris-Saclay（奥赛分子科学研究所（ISMO），法国国家科学研究中心，巴黎南大学，巴黎-萨克雷大学）
Imaging the coupling between itinerant electrons and localised moments in the centrosymmetric skyrmion magnet GdRu2Si2
磁skyrmion被认为是稳定的，只有在反演对称性破缺结构，但skyrmion晶格最近被发现在反演对称的Gd基化合物，刺激的stabilisationmechanism的问题。最近的一个理论建议，巡游电子和局部磁矩之间的耦合，是一个自然的结果，skyrmion是经得起检测，甚至使用非磁性探针，如光谱成像扫描隧道显微镜（SI-STM）。在这里，GdRu $_2$ Si $_2$的SI-STM观测揭示了局部态密度的模式，这些模式确实随底层磁性结构而变化。这些模式是定性再现模型计算假设巡回电子和本地化时刻之间的交换耦合。这些发现为理解GdRu $_2$ Si $_2$中skyrmion的形成机制提供了线索。
