The spin- and energy-dependent interface reflectivity of a ferromagnetic (FM) film in contact with a nonmagnetic (NM) film is calculated using a first-principles transport method and incorporated into the superdiffusive spin transport model to study the femtosecond laser-induced ultrafast demagnetization of $\mathrm{Fe}|\mathrm{NM}$ and $\mathrm{Ni}|\mathrm{NM}$ (NM = Au, Al, and Pt) bilayers. By comparing the calculated demagnetization with transparent and real interfaces, we demonstrate that the spin-dependent reflection of hot electrons has a noticeable influence on the ultrafast demagnetization and the associated terahertz (THz) electromagnetic radiation. In particular, a spin filtering effect is found at the $\mathrm{Fe}|\mathrm{NM}$ interface that increases the spin current injected into the NM metal, which enhances both the resulting demagnetization and the resulting THz emission. This suggests that the THz radiation can be optimized by tailoring the interface, indicating a very large tunability.

中文翻译：

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超快退磁和太赫兹发射中超扩散自旋电流的界面反射率

使用第一原理传输方法计算与非磁性（NM）膜接触的铁磁（FM）膜与自旋和能量相关的界面反射率，并将其结合到超扩散自旋输运模型中以研究飞秒激光诱导的超快消磁 $铁|\mathrm{NM}$ 和 $你|\mathrm{NM}$（NM = Au，Al和Pt）双层。通过将计算的退磁与透明和真实的界面进行比较，我们证明了热电子的自旋相关反射对超快退磁和相关的太赫兹（THz）电磁辐射具有显着影响。特别是，在$铁|\mathrm{NM}$该界面增加了注入到NM金属中的自旋电流，从而增强了产生的退磁和产生的THz发射。这表明可以通过调整界面来优化THz辐射，这表明可调性非常大。