Cheng Hao, Li Weiwei, Liu Zheng, Wang Yangkai, Wang Chengyue, Zhang Yiqian, Huang Qiuping, Lu Yalin
Hefei National Research Center for Physical Sciences at the Microscale & Anhui Laboratory of Advanced Photon Science and Technology, University of Science and Technology of China, Hefei 230026, China.
Department of Materials Science and Engineering, University of Science and Technology of China, Hefei, Anhui 230026, China.
ACS Appl Mater Interfaces. 2024 Oct 30;16(43):59597-59605. doi: 10.1021/acsami.4c13781. Epub 2024 Oct 21.
Spintronic THz emitters have been widely studied due to their advantages of broadband frequency, high efficiency, and easy fabrication. The spintronic THz signal is proportional to the magnetization of the ferromagnetic (FM) layer and requires an external magnetic field to maximize the THz signal intensity. Recently, a field-free emitter was designed based on a CoFeB/IrMn heterostructure via the exchange bias between two films. However, field-free spintronic THz emitters based on a common FM/nonmagnetic metal structure are rare. Here, we fabricate a tunable and field-free THz emitter with giant THz emission modulation ability based on a polyimide/CoFeB/Pt heterostructure. The THz emission can be modulated by changing the curvature radius of the polyimide substrate. After the emitter is forward bent, the THz radiation without an external magnetic field is stronger than in the flat state with a field, which we attribute to in-plane magnetic anisotropy on the FM layer induced by the tensile strain. When we curve the emitter backward, the THz intensity decreases sharply. Moreover, the modulation (Δ/) of the THz wave from the forward-curved and backward-curved emitter is over 95%, and the device shows good cyclic repeatability. We provide a novel way to design field-free spintronic THz sources, and flexible devices are promising for application in THz devices.
自旋电子太赫兹发射器因其宽带频率、高效率和易于制造等优点而受到广泛研究。自旋电子太赫兹信号与铁磁（FM）层的磁化强度成正比，并且需要外部磁场来使太赫兹信号强度最大化。最近，基于CoFeB/IrMn异质结构，通过两层薄膜之间的交换偏置设计了一种无外场发射器。然而，基于普通FM/非磁性金属结构的无外场自旋电子太赫兹发射器却很少见。在此，我们基于聚酰亚胺/CoFeB/Pt异质结构制造了一种具有巨大太赫兹发射调制能力的可调谐无外场太赫兹发射器。太赫兹发射可以通过改变聚酰亚胺衬底的曲率半径来调制。发射器向前弯曲后，无外部磁场时的太赫兹辐射比有磁场时的平坦状态更强，我们将其归因于拉伸应变在FM层上引起的面内磁各向异性。当我们将发射器向后弯曲时，太赫兹强度急剧下降。此外，来自向前弯曲和向后弯曲发射器的太赫兹波的调制（Δ/）超过95%，并且该器件表现出良好的循环重复性。我们提供了一种设计无外场自旋电子太赫兹源的新方法，柔性器件在太赫兹器件中的应用前景广阔。
