光，点亮飞秒磁学.pdfVIP

第37 卷 第S1 期 红 外 技 术 Vol.37 No.S1 2015 年12 月 Infrared Technology Dec. 2015  光，点亮飞秒磁学 何 为 （中国科学院物理研究所磁学国家重点实验室，北京 100190 ） 摘要：光和磁，或是说光和材料中的自旋间的相互作用，一直是物理学家关心的研究课题，被人们不 断挖掘出各种有趣的物理现象，并推动磁存储乃至整个磁学不断向前发展。随着自旋电子学器件工作 的频率越来越高，研究磁性材料中的超快自旋动力学成为当前研究热点。超快脉冲激光泵浦探测 （pump-probe ）的方法由于具有飞秒时间分辨，故而在磁性薄膜超快自旋动力学的研究中得到广泛应 用。近年来发现金属磁性材料被飞秒激光脉冲泵浦后，磁性材料的磁化强度迅速降低，甚至可能降为 0 ，从铁磁态转变到顺磁态，整个过程能在几百飞秒内完成，这种现象被称为超快退磁。飞秒激光脉 冲泵浦磁性材料导致的超快退磁现象蕴含丰富的物理内容，涉及到如电子、晶格和自旋间在非平衡态 下的量子多体相互作用等基本物理问题，从而开辟了磁学研究的一个新的方向-飞秒磁学。 关键词：光和自旋的相互作用；飞秒磁学；超快退磁；超快自旋流 中图分类号：TN219 文献标识码：A 文章编号：1001-8891(2015)S1-0001-08 Laser Lighting up Femtomagnetism HE Wei (State Key Laboratory of Magnetism, Chinese Academy of Sciences, Beijing 100190, China) Abstract ：The research of the interaction between photon and spin has been attracted a great of attention and has resulted a lot of interesting physical behaviors, which are to advance the development of the magnetic recording and magnetism. The study of spin dynamics in magnetic materials is one of key issues for the application of spintronics devices working in high frequency. The all-optical pump-probe method based on the femtosecond pulsed laser has been widely used in the exploring of spin dynamics due to its high time-resolved of 100 fs. When a laser pulse beats the ferromagnetic metal film, its magnetization drops down quickly in less than one picosecond. Such a behavior is called ‘ultrafast demagnetization ’. The ultrafast demagnetization is the result of the