We investigate picosecond spin currents across Au/iron-garnet interfaces in response to ultrafast laser heating of the electrons in the Au film. In the picoseconds after optical heating, interfacial spin currents occur due to an interfacial temperature difference between electrons in the metal and magnons in the insulator. We report measurements of this interfacial longitudinal spin Seebeck effect between Au and rare-earth iron-garnet insulators, i.e., $\mathrm{R}{\mathrm{E}}_3\mathrm{F}{\mathrm{e}}_5{\mathrm{O}}_{12}$, where RE is Y, Eu, Tb, Tm. By systematically varying the rare-earth element, we modify the total magnetic moment of the iron garnet. We use time-domain thermoreflectance measurements to characterize the thermal response of the bilayer to ultrafast optical heating. We use time-resolved magneto-optic Kerr effect measurements of the Au layer to measure the time evolution of spin accumulation in the Au film. Replacing Y with other rare earths enhances the electron-magnon conductance $G_{e-m}$ at the Au iron-garnet interface by as much as a factor of 3. The electron-magnon conductance does not follow the trend of either the total magnetization of the iron garnet or the magnetic moment of the rare earth.

中文翻译：

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Au和稀土铁石榴石双层中界面自旋塞贝克效应的超快测量

我们研究了 Au/铁-石榴石界面上的皮秒自旋电流，以响应 Au 膜中电子的超快激光加热。在光学加热后的皮秒内，由于金属中的电子和绝缘体中的磁振子之间的界面温差，会出现界面自旋电流。我们报告了 Au 和稀土铁石榴石绝缘体之间这种界面纵向自旋塞贝克效应的测量结果，即，$\mathrm{电阻}{\mathrm{乙}}_3\mathrm{F}{\mathrm{电子}}_5{\mathrm{哦}}_{12}$，其中 RE 是 Y、Eu、Tb、Tm。通过系统地改变稀土元素，我们修改了铁石榴石的总磁矩。我们使用时域热反射测量来表征双层对超快光学加热的热响应。我们使用 Au 层的时间分辨磁光克尔效应测量来测量 Au 膜中自旋积累的时间演变。用其他稀土代替 Y 增强电子磁子电导$G_{\mathrm{电子}-米}$ 在 Au 铁-石榴石界面处高达 3 倍。电子-磁振子电导不跟随铁石榴石的总磁化强度或稀土的磁矩的趋势。