Supercharged Terahertz Waves: An Advance with Magnetic Materials

A new magnetic material discovered at Tohoku University can generate terahertz waves of significantly greater intensity, offering a potential breakthrough in technologies ranging from medical imaging to security. Credit: SciTechDaily.com

Positioned between microwaves and infrared light, terahertz waves are key to pioneering advances in imaging and diagnostic technologies. A recent discovery at Tohoku University of a material that can emit these waves more intensely promises to catalyze significant advances in a spectrum of industries.

Terahertz waves are being intensively studied by researchers around the world seeking to understand the “terahertz gap”. Terahertz waves have a specific frequency that places them somewhere between microwaves and infrared light. This range is referred to as a “gap” because much remains unknown about these waves. In fact, it was only relatively recently that researchers were able to develop the technology to generate them. Researchers at Tohoku University have brought us closer to understanding these waves and filling this knowledge gap.

Advances in Terahertz Wave Generation

Researchers at the Advanced Materials Research Institute (WPI-AIMR) and the Graduate School of Engineering have discovered a new magnetic material that generates terahertz waves with an intensity about four times higher than that of typical magnetic materials.

Taking advantage of unique properties for terahertz waves, this technology is expected to be used in a variety of industrial fields, including imaging, medical diagnostics, safety inspection and biotechnology. Assistant Professor Ruma Mandal (WPI-AIMR) explains, “Terahertz waves are low the photo energies and unlike X-rays, they do not emit ionizing radiation. So if they are used for imaging or microscopy of patients, they may be less harmful to tissue or samples.

(a) Weyl magnet: schematic diagram of a Heusler cobalt–manganese–gallium (Co2MnGa) alloy crystal. (b) Light-induced terahertz waves. Credit: Shigemi Mizukami

Enhancing Terahertz Emission with Weyl Magnets

With these applications in mind, a team of researchers at Tohoku University set out to develop an efficient, compact, robust and cost-effective terahertz wave emitter. Weyl magnets—a type of topological material—have been shown to generate a large anomalous Hall effect that makes them suitable for generating terahertz waves. In this study, single-crystal thin film samples of a Weyl magnet made from a cobalt-manganese-gallium Heusler alloy were prepared and studied under different conditions.

(a) Photo-induced terahertz waves generated by the Weyl magnet: cobalt-manganese-gallium Heusler (Co2MnGa) thin film observed in this study. (b) Anomalous Hall effect observed in the corresponding thin film sample. Credit: Shigemi Mizukami

The Future of Terahertz Wave Research

It was found that the giant anomalous Hall effect originating from the topological electronic structure unique to Weyl magnets enhanced the photo-induced terahertz waves. This achievement will deepen our understanding of the interaction of light and spin in Weyl magnets.

“Although the intensity of the generated terahertz waves is still lower than that of spin-excited terahertz emitters developed to date,” says Professor Shigemi Mizukami, “the structure is simpler and expensive heavy metals such as platinum are no longer required “.

Mandal and their colleagues were able to experimentally demonstrate the ability of this magnetic material to produce terahertz waves, so that it could be used in spintronic devices and other important applications. Such a breakthrough in a fledgling field could shape the future of next-generation technologies.

This work was published in Asia NPG Materials on June 7, 2024.

Reference: “Topologically Influenced Terahertz Emission in Co₂ MnGa with a large anomalous Hall effect” by Ruma Mandal, Ren Momma, Kazuaki Ishibashi, Satoshi Iihama, Kazuya Suzuki and Shigemi Mizukami, 7 Jun 2024, Asia NPG Materials.
DOI: 10.1038/s41427-024-00545-9