光和微波驱动的FeGaB-BiSb界面自旋抽运
Light and microwave driven spin pumping across FeGaB-BiSb interface
摘要：
具有大自旋霍尔电导率的三维拓扑绝缘体（TI）已成为自旋电子学应用的潜在候选者。在这里，我们报告的自旋电荷转换在双层的非晶铁磁体（FM）Fe_{78} Ga_{13} B_{9}（FeGaB）和3-D TI Bi_{85} Sb_{15}（BiSb）激活两个互补的技术：自旋泵和超快自旋电流注入。直流磁化测量建立FeGaB薄膜的软磁特性，保持不变的FeGaB-BiSb的异质结构。宽带铁磁共振（FMR）研究表明，随着自旋角动量泄漏到TI层中，旋进磁化的阻尼增强，自旋混合电导值较大（5.03 x 10^{19} m^{-2}）。通过分析由反自旋霍尔效应在TI层上产生的磁场控制的双极直流电压，提取BiSb的自旋霍尔角和自旋扩散长度。由飞秒光脉冲诱导的太赫兹辐射测量得到的自旋抽运参数与铁磁共振结果一致。Kubo-Bastin公式和紧束缚模型计算揭示了TI膜的厚度依赖性自旋霍尔电导率，预测结果与实验数据非常吻合。我们的研究结果表明，室温沉积的非晶和多晶异质结提供了一个有前途的平台，创造新的自旋轨道扭矩器件。
英文摘要：
3-D topological insulators (TI) with large spin Hall conductivity have emerged as potential candidates for spintronic applications. Here, we report spin to charge conversion in bilayers of amorphous ferromagnet (FM) Fe_{78}Ga_{13}B_{9} (FeGaB) and 3-D TI Bi_{85}Sb_{15} (BiSb) activated by two complementary techniques: spin pumping and ultrafast spin-current injection. DC magnetization measurements establish the soft magnetic character of FeGaB films, which remains unaltered in the heterostructures of FeGaB-BiSb. Broadband ferromagnetic resonance (FMR) studies reveal enhanced damping of precessing magnetization and large value of spin mixing conductance (5.03 x 10^{19} m^{-2}) as the spin angular momentum leaks into the TI layer. Magnetic field controlled bipolar dc voltage generated across the TI layer by inverse spin Hall effect is analyzed to extract the values of spin Hall angle and spin diffusion length of BiSb. The spin pumping parameters derived from the measurements of the femtosecond light-pulse-induced terahertz emission are consistent with the result of FMR. Kubo-Bastin formula and tight-binding model calculations shed light on the thickness-dependent spin-Hall conductivity of the TI films, with predictions that are in remarkable agreement with the experimental data. Our results suggest that room temperature deposited amorphous and polycrystalline heterostructures provide a promising platform for creating novel spin orbit torque devices.
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