Erickson Adam, Zhang Qihan, Vakili Hamed, Li Chaozhong, Sarin Suchit, Lamichhane Suvechhya, Jia Lanxin, Fescenko Ilja, Schwartz Edward, Liou Sy-Hwang, Shield Jeffrey E, Chai Guozhi, Kovalev Alexey A, Chen Jingsheng, Laraoui Abdelghani
Department of Mechanical & Materials Engineering, University of Nebraska-Lincoln, 900 N 16th Street, W342 NH, Lincoln, Nebraska 68588, United States.
Department of Materials Science and Engineering, National University of Singapore, Block E2, #05-19, 5 Engineering Drive 2, Singapore 117579, Singapore.
ACS Nano. 2024 Nov 12;18(45):31261-31273. doi: 10.1021/acsnano.4c10145. Epub 2024 Oct 29.
Topologically protected magnetic skyrmions in magnetic materials are stabilized by an interfacial or bulk Dzyaloshinskii-Moriya interaction (DMI). Interfacial DMI decays with an increase of the magnetic layer thickness in just a few nanometers, and bulk DMI typically stabilizes magnetic skyrmions at low temperatures. Consequently, more flexibility in the manipulation of DMI is required for utilizing nanoscale skyrmions in energy-efficient memory and logic devices at room temperature (RT). Here, we demonstrate the observation of RT skyrmions stabilized by gradient DMI (g-DMI) in composition gradient-engineered CoPt single-layer films by employing the topological Hall effect, magnetic force microscopy, and nitrogen-vacancy scanning magnetometry. Skyrmions remain stable over a wide range of applied magnetic fields and are confirmed to be nearly Bloch-type from micromagnetic simulation and analytical magnetization reconstruction. Furthermore, we observe skyrmion pairs, which may be explained by skyrmion-antiskyrmion interactions. Our findings expand the family of magnetic materials hosting RT magnetic skyrmions by tuning g-DMI via gradient polarity and a choice of magnetic elements.
磁性材料中拓扑保护的磁斯格明子通过界面或体Dzyaloshinskii-Moriya相互作用（DMI）得以稳定。界面DMI在磁层厚度仅增加几纳米时就会衰减，而体DMI通常在低温下稳定磁斯格明子。因此，为了在室温（RT）下将纳米级斯格明子用于节能型存储器和逻辑器件，需要在DMI的操控上具有更大的灵活性。在此，我们通过利用拓扑霍尔效应、磁力显微镜和氮空位扫描磁强计，展示了在成分梯度工程化的CoPt单层薄膜中观察到由梯度DMI（g-DMI）稳定的室温斯格明子。斯格明子在很宽的外加磁场范围内保持稳定，并且通过微磁模拟和解析磁化重建证实其几乎为布洛赫型。此外，我们观察到了斯格明子对，这可能由斯格明子 - 反斯格明子相互作用来解释。我们的发现通过调整梯度极性和选择磁性元素来调节g-DMI，从而扩展了承载室温磁性斯格明子的磁性材料家族。
