纳米铁磁线磁畴壁本征棘轮效应的研究

The Netherlander J. H. Franken et al. reported a magnetic shift register based on ratchet effect of magnetic domain wall in Nature Nanotechnology in 2012. The proposed scheme has attracted much attention due to its possible application for magnetic racetrack memory proposed by S. Parkin, who is one of IBM fellows. In addition, the shift register can be functional with magnetic logic as well. It is considered that the magnetic shift register composed of ferromagnetic microring structures with the perpendicular anisotropy has many advantages, particularly such as low power consumption, longer device lifetime, high accuracy on nanometer scales, and unidirectional feature of magnetic domain wall propagation. However, the scheme has yet been realized unfortunately due to some drawbacks such as low operation speed and technical requirements for nano-fabrication. In our previous works based on micromagnetic simulations, we have discovered that the ratchet effect of magnetic domain wall, allowing the unidirectional propagation feature, can be achieved by an intrinsic correlation between the inner spin structure and dynamic behavior of magnetic domain wall. The discovered mechanism is found to effectively sustain soliton properties of the magnetic domain wall, to reduce the technical difficulty in manufacturing process, to increase the storage density, and to speed up the operational time on a sub-nanosecond timescale. The present project will adopts the theoretical approach combined with the experimental study of the intrinsic ratchet effect of magnetic domain wall, to reveal an underlying mechanism of the phenomenon and thus, to provide a fundamental understanding for disigning future functional devices based on the ratchet effect of magnetic domain wall. Through carrying out the proposed project, not only enhancing scientific knowledges, but also substantial contributions for practical applications in the field of spintronics are expected.

2012年荷兰的Franken等人在Nature Nanotechnology上报道了一种利用磁畴壁棘轮效应的磁移位寄存器。它不仅可与美国IBM的Parkin提出的磁赛道存储器相媲美而且兼有磁逻辑功能，引起了人们的关注。这种垂直各向异性微铁磁环移位寄存器不仅功耗低、寿命长而且有精准的磁畴壁定位性能和单向输运功能，但仍存在操控速度慢、制备工艺要求高、存储密度低等不足之处，离应用相差甚远。通过我们前期的微磁学模拟工作，我们认识到利用磁畴壁内部自旋结构与磁畴壁动力学行为之间的内在关联也可以实现纳米铁磁线磁畴壁的棘轮效应。这种方案可有效保持磁畴壁的孤立子性质、简化其制备工艺、提高存储密度、缩短操控周期接近亚纳秒量级。本课题将采用理论结合实验的方法，研究磁畴壁的本征棘轮效应并揭示其物理机制，并争取设计出具有实际应用价值的磁畴壁棘轮效应功能器件。本课题不仅具有科学研究意义而且有很好的应用前景。

2012年荷兰的Franken等人在Nature Nanotechnology上报道了一种利用磁畴壁棘轮效应的磁移位寄存器。它不仅可与美国IBM的Parkin提出的磁赛道存储器相媲美而且兼有磁逻辑功能。这种垂直各向异性微铁磁环移位寄存器不仅功耗低、寿命长而且有精准的磁畴壁定位性能和单向输运功能，但仍存在操控速度慢、制备工艺要求高、存储密度低等不足之处，离应用相差甚远。本项目在前期研究工作基础上，不仅在结构简单的圆柱形纳米铁磁线上实现了本征棘轮效应，而且在磁性量子点元胞自动机纳米结构中也实现了虚拟磁畴壁棘轮效应。此外，在周期性非对称结构进行图案化处理边缘的纳米铁磁线上也发现了一种棘轮式自旋波传播行为和选择性滤波行为。不仅如此，本项目采用理论结合实验的方法，研究了各种自旋电子学相关的物理现象和物理机制，并且这些研究工作基础上设计出了具有实际应用价值的基于磁畴壁动力学和磁动力学的各种磁功能器件，为未来自旋电子学应用设计提供了很好的参考。