反铁磁耦合结构的超快翻转机制研究

All Optical Switching (AOS) refers to the switching of magnetic states induced by ultrafast laser pulses. Thanks to the high switching speed and low energy consumption, AOS is viewed as one of the potential magnetic recording technologies. Since its discovery, AOS has drawn a lot of attention from the community. Our project studies the mechanisms of AOS in antiferromagnetically coupled multilayers. In such kind of structures, the thermal stability and interfacial spin polarization can be improved, whereas the interfacial antiferromagnetic coupling can be realized and easily tuned through interface engineering. In this project, the role of the rare-earth element will be analyzed through a systematic material study. The switching efficiency will be optimized by tuning the antiferromagnetic coupling between the two magnetic layers. Comprehensive understanding of the underlying physical mechanisms will help to design better the magnetic recording technique based on AOS, which paves the way for future high speed and low energy-consumption information storage technology.

磁性材料的磁状态受超快激光脉冲激发而产生翻转的效应称为全光翻转效应。全光翻转效应具有翻转速度快、能量消耗低等优点，可能成为未来自旋存储技术的数据写入手段，因而自发现以来受到了学术界的广泛关注。本项目研究反铁磁耦合多层膜结构中全光翻转效应的机制。反铁磁耦合多层膜结构可以有效地提高材料的热稳定性和界面自旋极化率，并且能够通过调控界面容易地调节界面反铁磁耦合强度。本项目将通过系统的材料研究来分析稀土磁矩在全光翻转效应中的作用，通过界面插层调控磁性层之间的反铁磁耦合，从而优化飞秒激光的翻转效率。理解稀土磁矩和反铁磁耦合在全光翻转效应中的作用将有助于实现全光翻转效应在器件中的应用，为实现未来高速、高效率、低能耗的自旋存储技术打好基础。

本项目主要研究磁性薄膜与飞秒激光之间的相互作用，重点探索稀土—过渡金属合金体系，其中两个磁子晶格以反铁磁方式耦合。本项目深入研究Gd基合金的全光翻转效应，发现了Gd元素对全光翻转效应的影响；进一步地，本项目将单脉冲全光翻转效应扩展到了无Gd元素的稀土—过渡金属合金体系，首次发现了不含Gd元素的CoTb合金的单脉冲翻转效应，且证明了其翻转机制不同于常规的Gd基体系中的单脉冲光翻转过程。本项目研究了人工反铁磁结构FM/Mo,W/FM体系中的超快动力学特征，发现了其低磁阻尼特性以及在器件方面的应用前景。此外，本项目还研究了磁性/非磁异质结的超快动力学特性以及相关的太赫兹发射效应，揭示了磁性/非磁异质结超快动力学过程与太赫兹发射过程之间的联系，通过光学设计优化了自旋太赫兹源辐射效率，揭示了参与太赫兹发射过程的各种发射机制。本项目的研究深入理解了Gd基合金的单脉冲翻转机制，首次利用单脉冲激光成功诱导无Gd元素的CoTb薄膜在几十个皮秒内实现磁矩翻转，扩展了单脉冲超快光翻转效应的材料选择范围，并且分析和优化自旋太赫兹的辐射效率，为自旋太赫兹技术的应用奠定基础。