Abstract We investigated the spin dynamics of a vortex state in a core-shell magnetic nanodisk driven by an oscillating field applied perpendicular to the disk plane by means of micromagnetic simulations. The nanodisk comprises a Py (Fe0.2Ni0.8) core of 100 nm in radius, surrounded by a 50 nm thick Fe shell. Fourier transform analyses show that the Py core and the Fe shell dominate spin-wave oscillation at the fundamental and higher order radial modes, respectively. For oscillating driving field tuned to the fundamental eigenfrequency, the Py/Fe interface effectively confines spin-wave excitation in the Py core region. This effect leads to significantly more rapid vortex core (VC) reversal in comparison to homogeneous disks. Our work demonstrates that the higher order modes can drive much faster VC reversal than the fundamental mode, in sharp contrast to the results obtained in homogeneous disks. With excitation levels up to 30 mT, we find strong nonlinear spin-wave dynamics in the system, which results in mode frequency redshifting, therefore the observation of the most rapid VC reversals below eigenfrequencies and VC switching in wide ranges of frequencies.

中文翻译：

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核壳磁性纳米盘中不寻常的自旋波动力学

摘要 我们通过微磁模拟研究了由垂直于磁盘平面施加的振荡场驱动的核壳磁性纳米盘中涡旋状态的自旋动力学。纳米盘包含半径为 100 nm 的 Py (Fe0.2Ni0.8) 核，周围是 50 nm 厚的 Fe 壳。傅里叶变换分析表明，Py 核和 Fe 壳分别在基频和高阶径向模式下主导自旋波振荡。对于调谐到基本特征频率的振荡驱动场，Py/Fe 界面有效地限制了 Py 核心区域的自旋波激发。与均质盘相比，这种效应导致涡核 (VC) 反转明显更快。我们的工作表明，高阶模式可以比基本模式驱动更快的 VC 反转，与在均质磁盘中获得的结果形成鲜明对比。在激发水平高达 30 mT 的情况下，我们发现系统中存在很强的非线性自旋波动力学，这导致模式频率红移，因此观察到低于本征频率的最快速 VC 反转和宽频率范围内的 VC 切换。