论文标题
通过超快THZ发射光谱法探测对COFEB/TA异质结构中自旋轨道偶联的大界面贡献
Probing of large interfacial contribution to spin orbit coupling in CoFeB/Ta heterostructure by ultrafast THz emission spectroscopy
论文作者
论文摘要
基于铁磁/非磁性双层异质结构的超快THZ辐射产生基于非磁性层内的自旋 - 电流的转换及其与铁磁层的界面。对于此类结构的THZ发射的基本机制，各种可能的子归因于不仅要研究材料特性本身的基本水平上的复杂性，还需要利用其对宽带和高功耗THZ发射的性能。在这里，我们报告了COFEB/TA双层在不同范围内不同的样品温度下的超快THZ发射，以揭示内在和外在旋转的作用，以充电转换过程。除了提高THZ的发射外，如果COFEB/TA样品在升高的温度下退火，则其温度依赖性还显示了THZ信号极性逆转。我们提取自旋大厅电阻率的行为，确定其内在的旋转厅电导率贡献，并将其与标准Fe/PT系统进行比较。我们的结果清楚地表明，在退火的COFEB/TA中，由修饰的界面产生的整体旋转霍尔角度的巨大界面贡献，其中在相应的旋转厅角中，符号反转从THZ振幅变化随温度变化而表现出来。
Ultrafast THz radiation generation from ferromagnetic/nonmagnetic bilayer heterostructure-based spintronic emitters generally exploits the conversion from spin- to charge-current within the nonmagnetic layer and its interface with the ferromagnetic layer. Various possible sub-contributions to the underlying mechanism of inverse spin Hall effect for the THz emission from such structures, need to be exploited for not only investigating the intricacies at the fundamental level in the material properties themselves but also for improving their performance for broadband and high-power THz emission. Here, we report ultrafast THz emission from CoFeB/Ta bilayer at varying sample temperatures in a large range to unravel the role of intrinsic and extrinsic spin to charge conversion processes. In addition to an enhancement in the THz emission, its temperature dependence shows a THz signal polarity reversal if the CoFeB/Ta sample is annealed at an elevated temperature. We extract the behaviour of the spin Hall resistivity, determine the intrinsic spin Hall conductivity contribution in it and compare those with the standard Fe/Pt system. Our results clearly demonstrate a giant interfacial contribution to the overall spin Hall angle arising from the modified interface in the annealed CoFeB/Ta, where a sign reversal in the corresponding spin Hall angle is manifested from the THz amplitude variation with the temperature.
