Magnetization dynamics of ferromagnetic rare earth metals induced by femtosecond laser excitation

该项目旨在对飞秒激光脉冲诱导的稀土铁磁体(Gd，Tb，Dy)的超快磁化动力学有一个基本的了解。利用时间分辨二次谐波探测和双光子光电子发射技术，研究了重稀土元素的磁光响应和非磁光响应的时间演化以及交换劈裂电子结构和电子分布。Gd(0001)表面的磁化动力学是一个理想的模型系统，它由(A)导致光激发的非平衡电子/自旋分布弛豫的非相干散射过程和(B)太赫兹频率范围内的相干磁化动力学所支配。Tb和Dy提出了前景看好的系统作为比较的测试案例。本项目的目标是：(1)系统地研究重稀土体系的超快磁化动力学。(Ii)在实验中探索的作为温度、激发密度和缺陷浓度的函数的光激发和随后的再磁化之后的几个100fs内有助于退磁的自旋散射机制的确定。(Iii)详细了解THz域中的相干磁化动力学，包括通过适当的基本过程描述阻尼。

The project aims at a fundamental understanding of ultrafast magnetization dynamics of rare earth ferromagnets (Gd, Tb, Dy) induced by femtosecond laser pulses. Time-resolved detection of second harmonic generation and two-photon-photoemission are employed as complementary experimental techniques to study the temporal evolution of the magnetic and non-magnetic optical response as well as the exchange-split electronic structure and electron distribution of heavy lanthanides. The magnetization dynamics on the Gd(0001) surface presents an ideal model system, which is governed by (a) incoherent scattering processes leading to relaxation of the photoexcited non-equilibrium electron/spin distribution and (b) coherent magnetization dynamics in the THz frequency range. Tb and Dy present promising systems as a test case for comparison. The goals of this project are: (i) Systematic study of ultrafast magnetization dynamics of heavy rare earth systems. (ii) Identification of spin-scattering mechanisms contributing to demagnetization within several 100 fs after the optical excitation and subsequent remagnetization probed in experiments as a function of temperature, excitation density and defect concentration. (iii) Detailed understanding of coherent magnetization dynamics in the THz domain including description of damping by appropriate elementary processes.