van der Waals (vdW) magnetic materials, such as Cr₂Ge₂Te₆ (CGT), show promise for memory and logic applications. This is due to their broadly tunable magnetic properties and the presence of topological magnetic features such as skyrmionic bubbles. A systematic study of thickness and oxidation effects on magnetic domain structures is important for designing devices and vdW heterostructures for practical applications. Here, we investigate thickness effects on magnetic properties, magnetic domains, and bubbles in oxidation-controlled CGT crystals. We find that CGT exposed to ambient conditions for 5 days forms an oxide layer approximately 5 nm thick. This oxidation leads to a significant increase in the oxidation state of the Cr ions, indicating a change in local magnetic properties. This is supported by real-space magnetic texture imaging through Lorentz transmission electron microscopy. By comparing the thickness-dependent saturation field of oxidized and pristine crystals, we find that oxidation leads to a nonmagnetic surface layer that is thicker than the oxide layer alone. We also find that the stripe domain width and skyrmionic bubble size are strongly affected by the crystal thickness in pristine crystals. These findings underscore the impact of thickness and surface oxidation on the properties of CGT, such as saturation field and domain/skyrmionic bubble size, and suggest a pathway for manipulating magnetic properties through a controlled oxidation process.

中文翻译：

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表面氧化和晶体厚度对Cr2Ge2Te6磁性能和磁畴结构的影响


范德瓦尔斯 (vdW) 磁性材料，例如 Cr ₂ Ge ₂ Te ₆ (CGT)，在内存和逻辑应用中显示出良好的前景。这是由于它们具有广泛可调的磁性以及拓扑磁性特征（例如斯格明离子气泡）的存在。磁畴结构的厚度和氧化效应的系统研究对于设计实际应用的器件和 vdW 异质结构非常重要。在这里，我们研究了氧化控制 CGT 晶体中厚度对磁性能、磁畴和气泡的影响。我们发现 CGT 暴露在环境条件下 5 天会形成约 5 nm 厚的氧化层。这种氧化导致 Cr 离子的氧化态显着增加，表明局部磁性发生变化。通过洛伦兹透射电子显微镜进行的真实空间磁性纹理成像支持了这一点。通过比较氧化晶体和原始晶体的厚度相关饱和场，我们发现氧化导致非磁性表面层比单独的氧化层更厚。我们还发现，条纹域宽度和斯格明子气泡尺寸受到原始晶体中晶体厚度的强烈影响。这些发现强调了厚度和表面氧化对 CGT 特性（例如饱和场和磁畴/斯格明离子气泡尺寸）的影响，并提出了通过受控氧化过程操纵磁性的途径。