Low power continuous-wave all-optical magnetic switching in ferromagnetic nanoarrays
Low power continuous-wave all-optical magnetic switching in ferromagnetic nanoarrays
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DOI：
10.1117/12.2633356
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发表时间：
2021-12
期刊：
影响因子：
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通讯作者：
K. Stenning;Xiaofei Xiao;Holly H. Holder;J. Gartside;A. Vanstone;O. Kennedy;R. Oulton;W. Branford
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文献类型：
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作者：
K. Stenning;Xiaofei Xiao;Holly H. Holder;J. Gartside;A. Vanstone;O. Kennedy;R. Oulton;W. Branford
全光磁开关有望实现超快、高分辨率的磁化控制，并具有无需磁场的技术吸引力。现有的全光开关方案由超快瞬态效应驱动，通常需要耗电的飞秒脉冲激光器和复杂的磁性材料。在这里，我们使用聚焦的低功率、线偏振连续波激光器演示了具有亚衍射极限尺寸的简单铁磁纳米磁体（Ni$_{81}$Fe$_{19}$、Ni$_{50}$Fe$_{50}$）中的确定性全光磁开关。孤立的纳米磁体可以在一系列尺寸、激光波长和功率之间切换。所有方形几何人工自旋冰顶点配置均已写入，包括功率低至 2.74 mW 的基态和能量不利的“类单极”状态。通常，线偏振光的磁开关是对称禁止的；然而，这里的激光光斑具有与纳米磁体相似的尺寸，产生取决于相对纳米岛光斑位移的吸收分布。我们将观察到的确定性切换归因于这种不对称吸收的瞬态动力学。在 Co 样品中没有观察到转变，这表明 NiFe 合金的多物种性质在逆转中发挥了作用。这里提出的结果带来了廉价、低功耗的光控设备，对数据存储、神经形态计算和可重构磁振子产生影响。
All-optical magnetic switching promises ultrafast, high-resolution magnetisation control with the technological attraction of requiring no magnetic field. Existing all-optical switching schemes are driven by ultrafast transient effects, typically requiring power-hungry femtosecond-pulsed lasers and complex magnetic materials. Here, we demonstrate deterministic, all-optical magnetic switching in simple ferromagnetic nanomagnets (Ni$_{81}$Fe$_{19}$, Ni$_{50}$Fe$_{50}$) with sub-diffraction limit dimensions using a focused low-power, linearly-polarised continuous-wave laser. Isolated nanomagnets are switched across a range of dimensions, laser wavelengths and powers. All square-geometry artificial spin ice vertex configurations are written, including ground-state and energetically-unfavourable `monopole-like' states at powers as low as 2.74 mW. Usually, magnetic switching with linearly polarised light is symmetry-forbidden; however, here the laser spot has a similar size to the nanomagnets, producing an absorption distribution dependent on the relative nanoisland-spot displacement. We attribute the observed deterministic switching to the transient dynamics of this asymmetric absorption. No switching is observed in Co samples, suggesting the multi-species nature of NiFe alloys plays a role in reversal. The results presented here usher in cheap, low-power optically-controlled devices with impact across data storage, neuromorphic computation and reconfigurable magnonics.