Kumar Sandeep, Kumar Sunil
Femtosecond Spectroscopy and Nonlinear Photonics Laboratory, Department of Physics, Indian Institute of Technology Delhi, New Delhi 110016, India.
iScience. 2022 Jul 4;25(8):104718. doi: 10.1016/j.isci.2022.104718. eCollection 2022 Aug 19.
Ultrafast THz radiation generation from ferromagnetic/nonmagnetic (FM/NM) spintronic heterostructures generally exploits the spin-charge conversion within the nonmagnetic layer and its interface with the ferromagnetic layer. Various possible sub-contributions to the underlying mechanism need to be exploited not only for 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,Fe)/(Ta,Pt) bilayers at varying sample temperatures to unravel the role of intrinsic and extrinsic spin-charge conversion processes through the extracted values of spin-Hall conductivities. An enhanced THz emission along with temperature-dependent THz signal polarity reversal is observed in the case of annealed CoFeB/Ta. These results demonstrate a large interfacial contribution to the overall spin-Hall angle arising from the modified interface in the annealed CoFeB/Ta.
从铁磁/非磁性（FM/NM）自旋电子异质结构中产生超快太赫兹辐射通常利用非磁性层及其与铁磁层界面处的自旋-电荷转换。不仅需要研究对潜在机制的各种可能的子贡献，以便在材料特性本身的基本层面上研究其复杂性，还需要研究如何提高它们在宽带和高功率太赫兹发射方面的性能。在这里，我们报告了在不同样品温度下（CoFeB,Fe）/（Ta,Pt）双层膜产生的超快太赫兹辐射，通过提取的自旋霍尔电导率值来揭示本征和非本征自旋-电荷转换过程的作用。在退火的CoFeB/Ta情况下观察到太赫兹发射增强以及太赫兹信号极性随温度反转。这些结果表明，退火后的CoFeB/Ta中改性界面在整体自旋霍尔角中起到了很大的界面贡献作用。
