fig. 1. Chiral molecules gain spin through thermal vibrations and adhere to magnets. Credit: Shinji Miwa / ISSP, University of Tokyo
A research group at the University of Tokyo has discovered a new principle by which helical serous molecules gain spin through molecular vibrations, enabling them to adhere to magnets. Until now, it was believed that chiral molecules could only exhibit magnetic properties when an electric current was applied. This discovery overturns conventional understanding.
Chiral molecules, which have a helical structure, are known to interact with magnets in a phenomenon known as chiral induced spin selectivity (CISS). For example, when a chiral molecule is attached to a magnet and an electric current is applied, magnetic effects can be observed. It has also been reported that magnets can be used to separate right-handed and left-handed chiral molecules.
The prevailing explanation is that the flow of current through a chiral molecule induces magnetic properties, similar to an electromagnet. However, this explanation has limitations, as it does not fully account for large magnetic effects or CISS phenomena even in the absence of electric current.
Professor Shinji Miwa of the University of Tokyo’s Institute for Solid State Physics, Nagoya University Professor Saksuko Ohto and a collaborative research team have developed a special electrochemical cell using spintronics technology for this study.
By varying the thickness of the gold film and analyzing the current change, oscillatory changes in intensity and sign were observed (Fig. 2C). These results indicate the presence of interlayer exchange coupling between the chiral molecules and the magnet.
Figure 2. (A) A schematic illustration of the experimental setup. (b) Representative results of magnetic measurements. The surface area of the working electrode was 0.5 mm2. The gray and green arrows in the figure represent the spin angular momentum (s) and its time derivative (DS/Dt), respectively. (c) MC ratio as a function of Au spacer thickness. (d) Schematic diagram of the computational model to represent the spin density. Yellow indicates up and cyan indicates down. Credit: Shinji Miwa / ISSP, University of Tokyo
To understand the mechanism behind coupling, it is important to determine how chiral molecules acquire magnetic properties in the absence of an electric current. The researchers found that the vibrational motion in the chiral molecules leads to the appearance of spins that depend entirely on chirality, regardless of the direction of the magnetic field. Fig. 2d shows the theoretical results of the first-principles calculations.
This study experimentally demonstrates that the CISS phenomenon arises from interlayer exchange coupling. Furthermore, it shows that chiral molecules can achieve spin and exhibit magnetic properties through molecular vibrations, without the need for an applied current. Because this mechanism does not rely on electrical current, it can occur globally in a variety of environments, including chemical reactions and biological processes.
This new insight is expected to lead to future research and applications in a wide range of fields, including chemistry and life sciences.
More information:
S. Miwa et al., Spin polarization driven by molecular vibrations leads to enantioselectivity in chiral molecules, Science advances (2025) doi: 10.1126/sciadv.adv5220
Provided by the University of Tokyo
Reference: Discovery of a new principle: Cheryl pursues innomagnets (2025, October 29).
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