Pulsed far-infrared radiation of ferromagnetic heterojunction and its photothermal regulation

作者：Xin-Bo Chu, Zuanming Jin, Xu Wu, Jingnan Li, Yang Shen, Ruoyu Wang, Bingyu Ji, Zhangshun Li, Yan Peng · 发表于：Acta Physica Sinica · 年份：2023 · DOI：10.7498/aps.72.20230543 · 被引用次数：2 · 研究领域：Advanced Memory and Neural Computing、Magnetic properties of thin films、Terahertz technology and applications

Under illumination of a femtosecond laser pulse on the Pt/CoFe/Ta trilayer heterostructure, an impulsive spin current can be generated in the ferromagnetic layer due to the ultrafast demagnetization. The spin current is super-diffusively transported and injected into the neighboring heavy metal layers, and is converted into the transversal charge current due to the spin-orbit coupling, which is named inverse spin Hall effect. The transient charge current on a time scale of sub-picosecond gives rise to the electromagnetic radiation in the far-infrared range to the free space. In this work, we demonstrate two kinds of experiments to investigate the modulation of far-infrared emission by photo-thermal effect, which is due to the thermal energy deposed by light pulses on a short timescales. First, the amplitude of the emitted far-infrared pulse as a function of an applied magnetic field is measured, which shows a far-infrared hysteresis behavior. The coercive field of the sample obtained by far-infrared hysteresis is smaller than that obtained by the <i>M</i>-<i>H</i> hysteresis through vibrating sample magnetometer. In addition, the coercive field decreases with pump laser fluence increasing. Second, the control of spin polarization on an ultrafast timescale in the presence of a small magnetic field applied oppositely to that of the magnetization of the ferromagnetic sample. The amplitude of far-infrared time-domain signal reaches a maximum value at a pum...