Abstract Magnetic skyrmions are topological chiral spin textures, which have potential application in storage-memory and other spintronic devices. Zero-field skyrmion and high-density skyrmion are the two most important aspects for the future skyrmion-based device applications. Here, we experimentally study the room temperature zero-field skyrmion and the evolution of high density skyrmion in [Pd/Co/Pd]N multilayer films from structure symmetry to asymmetry. The results show that the density of zero-field skyrmion can be adjusted by the number of cycles at the constant thickness of Co 0.4 nm. The maximum density ηSk, determined by Lorentz TEM observation, reaches 60 μm−2 in [Pd(3)/Co(1)/Pd(2)]15 multilayer film. We also found that the maximum density ηSk mainly occur in the reversible region of magnetization reversal by the first-order reversal curve (FORC) analysis. Interestingly, the polarity of zero-field skyrmion can be tuned by different MFM tips. The simulated results well confirm the experimental result. Our findings provide a pathway for designing the zero-field and high density skyrmion in magnetic multilayer films, which may apply for the development of skyrmion-based spintronic devices.

中文翻译：

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Pd/Co/Pd 多层膜中的室温零场和高密度 Skyrmions

摘要 磁性斯格明子是拓扑手征自旋结构，在存储存储器和其他自旋电子器件中具有潜在的应用价值。零场斯格明子和高密度斯格明子是未来基于斯格明子的设备应用的两个最重要的方面。在这里，我们通过实验研究了室温零场斯格明子和 [Pd/Co/Pd]N 多层膜中高密度斯格明子从结构对称到不对称的演变。结果表明，在Co 0.4 nm的恒定厚度下，零场skyrmion的密度可以通过循环数进行调整。由洛伦兹 TEM 观察确定的最大密度 ηSk 在 [Pd(3)/Co(1)/Pd(2)]15 多层膜中达到 60 μm-2。我们还通过一阶反转曲线（FORC）分析发现最大密度 ηSk 主要出现在磁化反转的可逆区域。有趣的是，零场斯格明子的极性可以通过不同的 MFM 尖端进行调整。模拟结果很好地证实了实验结果。我们的发现为设计磁性多层膜中的零场和高密度斯格明子提供了一条途径，这可能适用于基于斯格明子的自旋电子器件的开发。