Atomically thin graphene layers can act as a spin-sink material when adjacent to a nanoscale magnetic surface. The enhancement in the extrinsic spin–orbit coupling (SOC) strength of graphene plays an important role in absorbing the spin angular momentum injected from the magnetic surface after perturbation with an external stimulus. As a result, the dynamics of the excited spin system is modified within the magnetic layer. In this paper, we demonstrate the modulation of ultrafast magnetization dynamics at graphene/ferrimagnet interfaces using the time-resolved magneto-optical Kerr effect (TRMOKE) technique. Magnetically modified interfaces with a systematic increase in the number of graphene layers coupled with the 10 nm-thick Co₇₄Gd₂₆ layer are studied. We find that the variation in the dynamical parameters, i.e., ultrafast demagnetization time, remagnetization times, decay time, effective damping, precessional frequency, etc., observed at different time scales is interconnected. The demagnetization time and decay time for the ferrimagnet become approximately two times faster than the corresponding intrinsic values. We found a possible correlation between the demagnetization time and damping. The effect is more pronounced for the interfaces with monolayer graphene and graphite. The spin-mixing conductance is found to be approximately 0.8 × 10¹⁵ cm^–2. The effect of SOC, pure spin current, the appearance of structural defects, and thermal properties at the graphene/ferrimagnet interface are responsible for the modifications of several dynamical parameters. This work demonstrates some important properties of the graphene/ferrimagnet interface which may unravel the possibilities of designing spintronic devices with elevated performance in the future.

中文翻译：

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石墨烯/CoGd 界面的加速超快磁化动力学

当与纳米级磁性表面相邻时，原子级薄的石墨烯层可以充当自旋沉材料。石墨烯外在自旋轨道耦合 (SOC) 强度的增强在吸收外部刺激扰动后从磁表面注入的自旋角动量方面起着重要作用。结果，激发的自旋系统的动力学在磁性层内被修改。在本文中，我们使用时间分辨磁光克尔效应 (TRMOKE) 技术展示了石墨烯/亚铁磁体界面处超快磁化动力学的调制。磁性改性界面，系统增加石墨烯层数，加上 10 nm 厚的 Co ₇₄ Gd ₂₆层进行了研究。我们发现在不同时间尺度观察到的动力学参数，即超快退磁时间、再磁化时间、衰减时间、有效阻尼、进动频率等的变化是相互关联的。亚铁磁体的退磁时间和衰减时间变得比相应的固有值快大约两倍。我们发现退磁时间和阻尼之间可能存在相关性。对于具有单层石墨烯和石墨的界面，效果更为明显。发现自旋混合电导约为 0.8 × 10 ¹⁵ cm ^–2. SOC、纯自旋电流、结构缺陷的出现以及石墨烯/亚铁磁体界面处的热性能的影响是导致几个动力学参数发生变化的原因。这项工作展示了石墨烯/亚铁磁体界面的一些重要特性，这些特性可能揭示未来设计具有更高性能的自旋电子设备的可能性。