October 10, 2020
| By Zhang Liu | Copyedited by William, Zhang Liu
Recently, Terahertz Technology Innovation Research Institute achieved a series of research results in Terahertz field.
The institute made a breakthrough in magnetic modulation of terahertz waves and published a paper entitled “Magnetic Modulation of Terahertz Waves via Spin-Polarized Electron Tunneling Based on Magnetic Tunnel Junctions” in Area Ⅰ of Journal Physical Review Applied.
Magnetic tunnel junctions (MTJs) are a key technology in modern spintronics because they are the basis of read-heads of modern hard disk drives, nonvolatile magnetic random access memories, and sensor applications. In this paper, they demonstrate that tunneling magnetoresistance can influence terahertz (THz) wave propagation through a MTJ. In particular, various magnetic configurations between parallelstate and antiparallel state of the magnetizations of the ferromagnetic layers in the MTJ have the effect of changing the conductivity, making a functional modulation of the propagating THz electromagneticfields. Operating in the THz frequency range, a maximal modulation depth of 60% is reached for theparallel state of the MTJ with a thickness of 77.45 nm, using a magnetic field as low as 30 mT. TheTHz conductivity spectrum of the MTJ is governed by spin-dependent electron tunneling. It is anticipated that the MTJ device and its tunability scheme will have many potential applications in THz magneticmodulators, filtering, and sensing.
Link to the paper: https://journals.aps.org/prapplied/abstract/10.1103/PhysRevApplied.14.014032
In addition, an international research team composed of Terahertz Technology Innovation Research Institute of USST, Bielefeld University, Uppsala University, University of Strasbourg, Max Planck Institute, Swiss Federal Institute of Technology Zurich, and Free University of Berlin demonstrate a method of ultrafast terahertz (THz) magnetometry, which gives direct access to the (sub-)picosecond magnetization dynamics even in encapsulated materials or devices in a contact-free fashion, in a fully calibrated manner, and under ambient conditions. The relative research results were released in Journal Nature Communications. As a showcase for this powerful method, they measure the ultrafast magnetization dynamics in a laser-excited encapsulated iron film. Our measurements reveal and disentangle distinct contributions originating from (i) incoherent hot-magnon-driven magnetization quenching and (ii) coherent acoustically-driven modulation of the exchange interaction in iron, paving the way to technologies utilizing ultrafast heat-free control of magnetism. High sensitivity and relative ease of experimental arrangement highlight the promise of ultrafast THz magnetometry for both fundamental studies and the technological applications of magnetism.
Link to the paper: https://doi.org/10.1038/s41467-020-17935-6
Source from School of Optical-Electrical and Computer Engineering