偏振光诱导的[Pt/Co]_(3)MnIr薄膜中的电子自旋动力学研究

Study of polarized laser-induced ultrafast spin dynamics on[Pt/Co]_(3)MnIr film

使用时间分辨的磁光克尔泵浦探测系统,研究了铁磁-反铁磁(Ferromagnetism-Antiferromagnetism,FM-AFM)薄膜在不同偏振态的泵浦光激发下退磁信号的区别,以及光子角动量和激光热效应在泵浦探测过程中发挥的作用.基于逆法拉第效应,圆偏振光能够生成有效感应磁场,诱导电子轨道自旋定向.受光子携带角动量方向的影响,瞬态克尔峰的方向会发生改变,其方向与外磁场方向无关.通过改变MnIr层厚度的实验发现,顺磁电子的磁化是瞬态克尔峰的主要来源.这对未来进一步探索全光磁翻转中的自旋动力学机制具有重要意义.

In this study,ultrafast spin dynamics on FM-AFM(ferromagnetism-antiferromagnetism)thin film were explored using pump-probe technology with circularly polarized and linear pump beams.Circularly polarized light generates an effective inducting magnetic field,which is called the inverse Faraday effect.The direction of the transient Kerr peak only depends on the angular momentum of photons.The amplitude of the Kerr peak depends on the thickness of the MnIr film.This may be attributed to the fact that the transient Kerr peak originates from the magnetization of paramagnetic electrons.This study may help further the understanding of spin dynamics in HD-AOS(Helicity-Dependent All Optical Switching).