We report a study of magnetization reversals and skyrmion configurations in two systems, Pt/Co/MgO and Ir/Fe/Co/Pt multilayers, where magnetic skyrmions are stabilized by a combination of dipolar and Dzyaloshinskii–Moriya interactions (DMIs). The First Order Reversal Curve (FORC) diagrams of low-DMI Pt/Co/MgO and high-DMI Ir/Fe/Co/Pt exhibit stark differences, which are identified by micromagnetic simulations to be indicative of hybrid and pure Neel skyrmions, respectively. Tracking the evolution of FORC features in multilayers with dipolar interactions and DMI, we find that the negative FORC valley, typically accompanying the positive FORC peak near saturation, disappears under both reduced dipolar interactions and enhanced DMI. As these conditions favor the formation of pure Neel skyrmions, we propose that the resultant FORC feature—a single positive FORC peak near saturation—can act as a fingerprint for pure Neel skyrmions in multilayers. Our study thus expands on the utility of FORC analysis as a tool for characterizing spin topology in multilayer thin films.

中文翻译：

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多层薄膜中混合和纯 Néel 斯格明子的磁化反转特征

我们报告了两个系统中磁化反转和斯格明子配置的研究，Pt/Co/MgO 和 Ir/Fe/Co/Pt 多层，其中磁性斯格明子通过偶极和 Dzyaloshinskii-Moriya 相互作用（DMI）的组合稳定。低 DMI Pt/Co/MgO 和高 DMI Ir/Fe/Co/Pt 的一阶反转曲线 (FORC) 图表现出明显的差异，通过微磁模拟确定，分别表示混合和纯尼尔斯格明子. 跟踪具有偶极相互作用和 DMI 的多层中 FORC 特征的演变，我们发现负 FORC 谷，通常伴随着接近饱和的正 FORC 峰，在减少偶极相互作用和增强 DMI 下消失。由于这些条件有利于纯尼尔斯格明子的形成，我们建议由此产生的 FORC 特征——接近饱和的单个正 FORC 峰——可以作为多层中纯尼尔斯格明子的指纹。因此，我们的研究扩展了 FORC 分析作为表征多层薄膜中自旋拓扑的工具的实用性。