基于超快X射线衍射的铁电/铁磁异质结瞬态结构动力学研究

磁电耦合效应等物理特性赋予了多铁材料广阔的潜在应用前景。然而，尽管飞秒激光脉冲提供了崭新的磁电调控手段，目前对多铁材料的动力学性质和光致磁电耦合机制的了解仍然有限。桌面型超快X射线衍射同时提供了亚皮秒时间分辨和毫埃量级结构变化解析能力，可为研究光致磁电耦合机制提供直接的结构动力学证据。本项目拟针对铁电/铁磁异质结中的光致磁电响应过程，利用超快X射线衍射直接探测飞秒激光辐照下铁磁层和铁电层的瞬态结构演化。同时，通过测量铁磁层的去磁化速度、异质结界面的能量传递速度、铁电层的压电响应速度等关键因素，分析铁磁层材料、温度、衬底等对光致磁电耦合速度的影响，从而在超快时域上深入理解对应的光致磁电耦合机制。

Multiferroic materials exhibit unusual physical properties such as magnetoelectric coupling effect, which in turn promise new device applications, while femtosecond optical pulses offer a new and ultrafast route to control their magnetoelectric coupling. However, our understanding to the dynamics and mechanism of photo-induced magnetoelectric coupling is still limited. With simultaneous subpicosecond temporal and mili-Angstrom spatial resolutions, table-top ultrafast x-ray diffraction will provide direct evidences on structural dynamics in order to understand the photo-induced magnetoelectric coupling mechanism. Here, we propose to investigate the ultrafast structural dynamics of a ferroelectric/ferromagnet heterostructure after femtosecond laser illumination by ultrafast x-ray diffraction. We plan to measure the demagnetization speed of the ferromagnet layer, the piezoelectric effect of the ferroelectric layer and the interplay between two thin layers. In addition, the influence of the ferromagnet material, temperature and substrate on the speed of the magnetoelectric coupling process will be evaluated experimentally. All these experimental studies may help us to distinguish between strain-mediated and charge-mediated mechanisms in time domain.