Spintronic THz Emitters

Spintronic THz Emitters
Figure (a): THz transients generated by the spintronic THz emitter containing exchange-coupled FM layers (Fe) for two magnetic fields µ0H = ±8 mT applied parallel to the emitter surface. (b) Power spectra of the transients shown in (a), for magnetic field µ0H = +8 mT (red) and µ0H = -8 mT (grey). (c) Variation of THz maximum peak amplitude generated by a MgO//Fe/Pt/Cr/FePt spintronic emitter pair for tCr = 1.7 nm. The displayed trace shows up to 300% THz signal enhancement at magnetic fields close to µ0H = ±8 mT due to the antiparallel alignment of magnetization in the two Fe layers at this field, compared to the parallel alignment in a saturation. Inset in (c) shows the shematics of the THz emitter pair with the incident laser pulse (red waveform) and the generated THz beam (blue waveform).

In this project, we employ laser pulses in order to generate superdiffusive spin currents (JS) in a variety of ferromagnet /normal-metal (FM/NM) layered structures. Due to the spin-orbit coupling in the NM layers, electrons with opposite spin are deflected into opposite directions and create a overall charge current density JC ∝ DISHE (JS × σ), where DISHE is the spin Hall angle and σ is the spin polarization of JS. Triggering this process by femtosecond laser pulses results in bursts of charge currents JC leading to the emission of electromagnetic transients, which show a frequency content extending up into the terahertz (THz) frequency range. Detailed knowledge of the working principles of the spintronic THz emitters is expected to lead to a better understanding of the dynamics of the spin-to-charge and charge-to-spin conversion mechanisms. In addition, due to their robustness, tunability and simplicity, spintronic THz emitter structures have a potential to be applied in a broad range of high-tech fields, including physics, chemistry, medicine, security, data handling and communication.

Publications

R. Adam, D. Cao, D. E. Bürgler, S. Heidtfeld, F. Wang, C. Greb, J. Cheng, D. Chakraborty, I. Komissarov, M. Büscher, M. Mikulics, H. Hardtdegen, R. Sobolewski, and C. M. Schneider, THz generation by exchange-coupled spintronic emitters, npj Spintronics 2, 58 (2024)
https://doi.org/10.1038/s44306-024-00061-0

J. Cheng, I. Komissarov, G. Chen, D. Chakraborty, R. Adam, D. E. Bürgler, S. Heidtfeld, D. Cao, M. Büscher, H. Hardtdegen, M. Mikulics, C. M. Schneider, L. Gladczuk, P. Przyslupski, and R. Sobolewski, Terahertz inverse spin Hall effect in spintronic nanostructures with various ferromagnetic materials, Journal of Magnetism and Magnetic Materials, 593, 171641 (2024)
https://doi.org/10.1016/j.jmmm.2023.171641

M. Mikulics, R. Adam, G. Chen, D. Chakraborty, J. Cheng, A. Pericolo, I. Komissarov, D. E. Bürgler, S. F. Heidtfeld, J. Serafini, S. Preble, R. Sobolewski, C. M. Schneider, J. Mayer, and H. H. Hardtdegen, Determination of thermal damage threshold in thz photomixers using Raman spectroscopy, Crystals 13, 10.3390/cryst13081267 (2023)
https://doi.org/10.3390/cryst13081267

S. Heidtfeld, R. Adam, T. Kubota, K. Takanashi, D. Cao, C. Schmitz-Antoniak, D. E. Bürgler, F. Wang, C. Greb, G. Chen, I. Komissarov, H. Hardtdegen, M. Mikulics, R. Sobolewski, S. Suga, and C. M. Schneider, Generation of terahertz transients from Co2Fe0.4Mn0.6Si Heusler alloy/heavy-metal bilayers, Journal of Magnetism and Magnetic Materials 547, 168791 (2022)
https://doi.org/10.1016/j.jmmm.2021.168791

G. Chen, D. Chakraborty, J. Cheng, M. Mikulics, I. Komissarov, R. Adam, D. E. Bürgler,
C. M. Schneider, H. Hardtdegen, and R. Sobolewski, Transient THz emission and effective mass determination in highly resistive GaAs crystals excited by femtosecond optical pulses, Crystals 12 (2022)
https://doi.org/10.3390/cryst12111635

S. Heidtfeld, R. Adam, T. Kubota, K. Takanashi, D. Cao, C. Schmitz-Antoniak, D. E. Bürgler, F. Wang, C. Greb, G. Chen, I. Komissarov, H. Hardtdegen, M. Mikulics, R. Sobolewski, S. Suga, and C. M. Schneider, Generation of terahertz transients from Co2Fe0.4Mn0.6Si Heusler alloy/normal-metal nanobilayers excited by femtosecond optical pulses, Phys. Rev. Research 3, 043025 (2021)
https://doi.org/10.1103/PhysRevResearch.3.043025

R. Adam, G. Chen, D. E. Bürgler, T. Shou, I. Komissarov, S. Heidtfeld, H. Hardtdegen,
M. Mikulics, C. M. Schneider, and R. Sobolewski, Magnetically and optically tunable terahertz radiation from Ta/NiFe/Pt spintronic nanolayers generated by femtosecond laser pulses, Applied Physics Letters 114, 212405 (2019)
https://doi.org/10.1063/1.5099201

Last Modified: 11.02.2025