Schematic diagrams of classical mechanical spin pumping (a) and quantum mechanical spin pumping (b). /Courtesy of the Ministry of Science and ICT

Domestic researchers have proven the phenomenon of quantum mechanical spin pumping occurring at room temperature for the first time in the world. Spin pumping is attracting attention as an innovative current generation technique.

The Ministry of Science and ICT noted on the 30th that a joint research team led by Professor Jeong Myung-hwa from Sogang University and Professors Lee Kyung-jin and Kim Gap-jin from the Korea Advanced Institute of Science and Technology (KAIST) has discovered the phenomenon of quantum mechanical spin pumping at room temperature for the first time in the world. The research, supported by the Ministry of Science and ICT's basic research projects, was published on the 29th (local time) in the international journal "Nature."

Electrons possess both the electric property of charge and the magnetic property of spin simultaneously. Current is divided into charge current, which occurs from the movement of charge, and spin current, which arises from the movement of spin. Most of the electronic devices we use operate on charge current. Spin refers to the intrinsic property of particles and the momentum of rotating objects.

Charge current has the issue that when current flows, electrons collide with atoms inside the material, generating heat and increasing energy consumption, which lowers the efficiency of current generation.

To address this, researchers worldwide are conducting studies on creating electronic devices using spin current. This is referred to as "spintronics." The key to implementing spintronics technology is generating spin current. When spin is moved, current is generated.

The research team focused on the spin pumping phenomenon where spin moves from a ferromagnet to a non-magnetic material due to precession.

Professor Jeong's research team predicted that it would be possible to implement the spin pumping phenomenon quantum mechanically. The team produced iron (Fe)-rhodium (Rh) ferromagnetic thin films and, in collaboration with Professor Kim Gap-jin's team, observed large spin currents utilizing the properties of the thin films. Professor Lee Kyung-jin's team interpreted this using quantum mechanical theory and proved it through additional experiments.

Most quantum mechanical phenomena have only been observed at very low temperatures, but this research is significant as it observed spin pumping phenomena at room temperature for the first time in the world. Furthermore, since it proposed a method that generates more than ten times the spin current compared to existing classical mechanical methods, it is expected to contribute to the development of next-generation electronic devices.

The research team evaluated, "Unlike previous spintronics research that interpreted magnetization from a classical mechanical perspective, this proves that a quantum mechanical approach is essential in spintronics," adding, "It holds significant implications showing that spintronics technology could serve as a key foundation for quantum technology."