单次激发IR泵浦共振X射线散射探针实验中铁磁有序条畴的不可逆转变
Irreversible transformation of ferromagnetic ordered stripe domains in single-shot IR pump - resonant X-ray scattering probe experiments
摘要：
在自由电子激光（LCLS）X射线（X-ray）LCLS上，利用单次激发的时间分辨共振X射线散射研究了强飞秒红光（IR）激光脉冲激发下磁畴结构的演化。一个良好有序的条纹域图案，目前在薄CoPd合金膜已被用作原型磁畴结构的这项研究。IR激光泵浦脉冲的能量密度足以导致在IR激光泵浦脉冲激励后的前几百飞秒内发生的超快退磁过程中的磁化几乎完全淬灭。在较长的时间尺度上，这种激励引起了随后的磁畴结构的不可逆转变。在我们特定的实验条件下，磁化开始恢复大约需要2纳秒。在大约5纳秒之后，先前有序的条纹畴结构已经演变成无序的迷宫畴结构。令人惊讶的是，我们观察到约7纳秒后发生的部分有序的条纹域结构重新定向到一个新的方向。正是在这种畴结构中，样品的磁化强度稳定下来，正如在最初的泵浦-探测循环之后很久记录的散射图案所揭示的那样。使用微磁模拟，我们可以解释这种观察的基础上的变化的磁各向异性随着热耗散的薄膜。
英文摘要：
The evolution of a magnetic domain structure upon excitation by an intense, femtosecond Infra-Red (IR) laser pulse has been investigated using single-shot based time-resolved resonant X-ray scattering at the X-ray Free Electron laser LCLS. A well-ordered stripe domain pattern as present in a thin CoPd alloy film has been used as prototype magnetic domain structure for this study. The fluence of the IR laser pump pulse was sufficient to lead to an almost complete quenching of the magnetization within the ultrafast demagnetization process taking place within the first few hundreds of femtoseconds following the IR laser pump pulse excitation. On longer time scales this excitation gave rise to subsequent irreversible transformations of the magnetic domain structure. Under our specific experimental conditions, it took about 2 nanoseconds before the magnetization started to recover. After about 5 nanoseconds the previously ordered stripe domain structure had evolved into a disordered labyrinth domain structure. Surprisingly, we observe after about 7 nanoseconds the occurrence of a partially ordered stripe domain structure reoriented into a novel direction. It is this domain structure in which the sample's magnetization stabilizes as revealed by scattering patterns recorded long after the initial pump-probe cycle. Using micro-magnetic simulations we can explain this observation based on changes of the magnetic anisotropy going along with heat dissipation in the film.
机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。
