[Science Column] Korean Researchers Succeed in Controlling Spin with World’s First New Nanohelix Structure

Spin Control in Chiral Magnetic Nanohelices
Pioneering Room-Temperature Spintronics Without External Magnetic Fields
Breakthrough by Kim Younggeun and Nam Kitae Teams Published in Science

A team of Korean researchers has, for the first time in the world, created a new type of magnetic nanohelix structure capable of controlling the spin direction of electrons without the need for an external magnetic field or ultra-low temperature devices. They have also developed a technology that selectively transports spins using this nanostructure.

The Ministry of Science and ICT announced that a research team led by Professor Kim Younggeun at Korea University (with Dr. Jeon Yoosang and researcher Jeong Eunjin as first authors) and a team led by Professor Nam Kitae at Seoul National University have fabricated a magnetic "chiral helical structure" and confirmed that spin can be controlled across a wide temperature range, including at room temperature.

Schematic diagram of chiral magnetic nanohelices. The research team controlled the twisted direction of the chiral molecules adsorbed on the metal particle surface to the right- or left-handed chiral direction by adding chiral molecules during the crystallization process of particles while reducing metal ions electrochemically. Provided by the research team

A chiral structure is one that cannot be superimposed on its mirror image, much like right and left hands. Clockwise and counterclockwise helical rotations are representative examples of chiral structures, and depending on chirality, substances with the same composition can exhibit completely different properties.

"Spintronics" technology, which uses the spin state of electrons to store, process, and transmit information, hinges on the ability to control and detect spin. This technology is a core component of magnetic memory (MRAM), a type of non-volatile memory where information remains even when the power is off, and is drawing attention as a next-generation information device technology.

The research team succeeded in fabricating a "chiral magnetic nanohelix structure" by electrochemically controlling the metal crystallization process. During this process, they introduced small amounts of chiral organic molecules (cinchonine and cinchonidine) to induce the helix to twist in the desired direction, which is a very rare achievement for inorganic materials.

In these chiral magnetic nanohelix structures, the team experimentally demonstrated that only specific spins pass through easily, while spins in the opposite direction are blocked. This is the first result to reveal that the inherent rotational nature of the three-dimensional nanohelix structure can selectively filter and transport spins. Additionally, thanks to the intrinsic magnetism of the magnetic nanohelix, they confirmed that spins passing through this structure can travel long distances even at room temperature.

Furthermore, the team developed a new method to quantitatively confirm chirality by utilizing the property of the nanohelix to generate its own voltage (electromotive force) while rotating in a magnetic field.

Professor Kim Younggeun explained, "Magnetic materials inherently have the ability to align electron spins, making it possible to control the flow of spins through chiral structures. This research provides a deeper understanding of the principles of chiral spintronics, which have so far been reported in theory and experiment."

Professor Nam Kitae emphasized, "Unlike organic materials, controlling chirality at the nanoscale in metals is a significant scientific challenge. This is the first result to control the twisted directionality of helices using molecules."

This research was published on September 5 (local time, September 4, 2:00 p.m. Eastern Time (ET)) in the world-renowned international journal Science. (Paper title: Spin-selective transport through chiral ferromagnetic nanohelices)