Magnetization reversal driven by low dimensional chaos in a nanoscale ferromagnet
Magnetization reversal driven by low dimensional chaos in a nanoscale ferromagnet
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DOI：
10.1038/s41467-019-08444-2
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发表时间：
2019-02-01
影响因子：
16.6
通讯作者：
Krivorotov, Ilya N.
中科院分区：
文献类型：
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作者：
Montoya, Eric Arturo;Perna, Salvatore;Krivorotov, Ilya N.
能量高效的磁化转换是非易失性磁存储和磁神经形态计算的核心问题。在过去的二十年里，人们展示了几种有效的磁开关方法，包括自旋力矩、磁电和微波辅助开关机制。实验表明，交变自旋扭矩引起的低维磁混沌能显著提高纳米铁磁体的热激活磁开关速率。该机构在自旋扭矩幅值上表现出明显的阈值特性，其效率随自旋扭矩频率的降低而提高。我们给出了分析和数值计算，定量地解释了这些实验结果，并揭示了鞍点平衡附近的低维磁混沌在提高开关速率方面所起的关键作用。我们的工作揭示了磁纳米系统能量辅助开关中混沌和随机性之间的重要相互作用，并为提高自旋扭矩记忆和逻辑的能效铺平了道路。
Energy-efficient switching of magnetization is a central problem in nonvolatile magnetic storage and magnetic neuromorphic computing. In the past two decades, several efficient methods of magnetic switching were demonstrated including spin torque, magneto-electric, and microwave-assisted switching mechanisms. Here we experimentally show that low-dimensional magnetic chaos induced by alternating spin torque can strongly increase the rate of thermally-activated magnetic switching in a nanoscale ferromagnet. This mechanism exhibits a well-pronounced threshold character in spin torque amplitude and its efficiency increases with decreasing spin torque frequency. We present analytical and numerical calculations that quantitatively explain these experimental findings and reveal the key role played by low-dimensional magnetic chaos near saddle equilibria in enhancement of the switching rate. Our work unveils an important interplay between chaos and stochasticity in the energy assisted switching of magnetic nanosystems and paves the way towards improved energy efficiency of spin torque memory and logic.