Ultrafast Demagnetization Dominates Fluence Dependence of Magnetic Scattering at Co M Edges.
Ultrafast Demagnetization Dominates Fluence Dependence of Magnetic Scattering at Co M Edges.
复制标题
超快退磁主导 Co M 边缘磁散射的通量依赖性。
DOI：
--
复制
发表时间：
2020
影响因子：
8.6
通讯作者：
S. Eisebitt
中科院分区：
文献类型：
--
作者：
Michael Schneider;B. Pfau;C. Günther;C. von Korff Schmising;D. Weder;J. Geilhufe;J. Perron;F. Capotondi;E. Pedersoli;M. Manfredda;M. Hennecke;B. Vodungbo;J. Lüning;S. Eisebitt
系统地研究了Co/Pd多层膜中磁畴共振散射截面的注量依赖性。利用FERMI@Elettra自由电子激光器，用飞秒量级的单脉冲极紫外光（XUV）探测样品，并将其调谐到Co M_{3，2}吸收共振。我们报告的定量数据超过3个数量级的通量，涵盖16 mJ/cm^{2}/脉冲至10 000 mJ/cm^{2}/脉冲，脉冲长度为70 fs和120 fs。观察到衍射截面随能量密度的逐渐淬灭。将相同的脉冲能量压缩成较短的脉冲，即XUV峰值电场增大，导致Co M_{3，2}边共振衍射的猝灭减弱。我们的结论是淬火效应观察到的共振散射涉及短寿命的钴3 p核心空缺是非相干的性质。这一发现是在以前的报告调查共振散射涉及寿命较长的钴2 p状态，受激发射已被发现是重要的。一个唯象模型的基础上XUV诱导的超快退磁是能够再现我们的整个实验数据集，并被发现是一致的与独立的磁光测量的退磁动力学相同的样品。
We systematically study the fluence dependence of the resonant scattering cross-section from magnetic domains in Co/Pd-based multilayers. Samples are probed with single extreme ultraviolet (XUV) pulses of femtosecond duration tuned to the Co M_{3,2} absorption resonances using the FERMI@Elettra free-electron laser. We report quantitative data over 3 orders of magnitude in fluence, covering 16 mJ/cm^{2}/pulse to 10 000 mJ/cm^{2}/pulse with pulse lengths of 70 fs and 120 fs. A progressive quenching of the diffraction cross-section with fluence is observed. Compression of the same pulse energy into a shorter pulse-implying an increased XUV peak electric field-results in a reduced quenching of the resonant diffraction at the Co M_{3,2} edge. We conclude that the quenching effect observed for resonant scattering involving the short-lived Co 3p core vacancies is noncoherent in nature. This finding is in contrast to previous reports investigating resonant scattering involving the longer-lived Co 2p states, where stimulated emission has been found to be important. A phenomenological model based on XUV-induced ultrafast demagnetization is able to reproduce our entire set of experimental data and is found to be consistent with independent magneto-optical measurements of the demagnetization dynamics on the same samples.