[Reading Science] Future-Changing 'Spintronics'... Magnets Determine Gukun's Fate

Key Core Materials of the 4th Industrial Revolution
Essential for Data Management and Electric Vehicles
Countries Worldwide Accelerate Development of Affordable and Powerful Permanent Magnets

Magnets are familiar as childhood toys. However, they are also essential "national core future materials" in the era of the Fourth Industrial Revolution. They are indispensable in most advanced fields, from electric vehicle motors to data storage and reading. Scientists worldwide are continuously researching to create magnets that are stronger, more efficient, and cheaper. Since rare earth elements, which are key materials and a core point of conflict in the US-China technological hegemony, are involved, researching new technologies is essential to secure a stable supply chain.

What is a Magnet?

Magnets exist naturally and have been used in devices like compasses. William Gilbert (1544?1633), an English physician, hypothesized that the reason the north pole points north is because the Earth itself is a magnet, a theory later accepted. However, the Earth's magnetic field reverses its north and south poles every several hundred thousand years, and the magnetic field varies by location. The exact cause of why the Earth has magnetism is still not fully understood. Danish scientist Hans Christian Ørsted (1777?1851) discovered that electric current generates a magnetic field, and Michael Faraday (1791?1867), a famous British chemist and physicist who discovered benzene, revealed that moving a magnet produces electricity.

The magnetic field originates from the force of electrons spinning and revolving around the atomic nucleus. It is fundamentally the same as electric current. If current is electrons energized and flowing out of their original positions, then the magnetic field is generated by electrons spinning and revolving. Therefore, basically all atoms can be considered to have magnetic properties. They are classified by magnetic strength into ferromagnetic, paramagnetic, and diamagnetic materials. The stronger the magnetic force, the better the electrons’ spins are aligned in the same direction; the weaker, the more disordered they are. However, some materials like copper or plastic have no magnetism at all due to their atomic properties. The strength of magnetism is determined by temperature and the distance between atoms. Higher temperatures weaken magnetism as electron movements become random. Near absolute zero (?273°C), electron movements become orderly and aligned, exhibiting magnetism. The distance between atoms also affects magnetism; it must be neither too close nor too far for easy electron alignment.

Scientists have been striving for over 100 years to create artificial permanent magnets. Ferrite magnets made mainly of iron oxides were developed in the 1940s, Alnico magnets made of aluminum, nickel, and cobalt in the 1950s, and samarium-cobalt (Sm-Co) magnets in the 1970s. However, the use of expensive rare metals like cobalt limited mass production and commercialization. Then, in 1981, Masato Sagawa from Japan developed the powerful and inexpensive neodymium (Nd-Fe-B) magnet, enabling magnet use in various industrial products. He mixed iron with rare earth neodymium and boron. Iron was initially known as a material that could not produce strong magnets because atoms were too close. Sagawa inserted small, light boron atoms between iron atoms and found the golden ratio with neodymium to induce electron alignment, successfully creating the strongest magnet ever. However, this magnet’s performance drops at high temperatures (around 200°C). Mixing another rare earth, dysprosium (Dy), can improve this drawback.

Spintronics Changing the Future

Spintronics is the study of what happens when electrons with spin move. It involves researching various changes caused by electric current flowing through magnets and applying this to advanced technologies like computer hard disks and semiconductors. Research began in earnest with the emergence of nano technology in the 1980s, which allowed manipulation of ultra-fine materials. Scientists tried to build artificial magnets by stacking atoms layer by layer. Initially, they used the principle that increasing the distance between atoms could create stronger magnets by adding a layer of atoms between magnets. This seemed successful as the magnets became stronger. However, when two layers of atoms were stacked, a phenomenon called interlayer exchange coupling occurred, where the upper and lower magnets switched positions repeatedly. This was the "Giant Magneto Resistive effect" (GMR) discovered by Peter Gr?nberg and Albert Fert in 1988. The magnetic head applying this effect is the core technology of modern computer hard disks. Hard disk platters store digital information as N pole 1 and S pole 0. The magnetic head has two small magnets installed vertically; the upper magnet is fixed as the N pole, and the lower magnet alternately contacts the N and S poles on the platter, causing parallel and antiparallel states repeatedly. Resistance increases and decreases each time, allowing digital data to be read. Professor Kim Gapjin of KAIST’s Department of Physics explained, "Data is the core of the Fourth Industrial Revolution, and magnets are the means to store and read it. Developing and utilizing high-performance magnets is a key task in advanced future industries like semiconductors and electric vehicles."

National Core Future Material

Currently, the rare earth neodymium used in commercial neodymium magnets is mainly extracted through complex processes from monazite and bastnasite ores. Due to severe environmental pollution and labor-intensive processes, China produces most of the global supply like other rare earths. As US-China technological hegemony competition intensifies and global supply chains become unstable, the need to replace or supplement Chinese neodymium is growing. South Korea is also set to commercialize technology developed through a 2021 national R&D project that can replace 30% of neodymium in permanent magnets with cheaper cerium (Ce), a rare earth element.

In this regard, in March, a research team at the Korea Institute of Materials Science revealed specific details. They succeeded in developing rare earth-reduced permanent magnet material technology that reduces the use of expensive rare earth neodymium (Nd) by about 30% while achieving performance comparable to commercial magnets (grade 42M). Instead of conventional processes, they applied melt-spinning and hot-deformation methods, which allow very rapid cooling, to rare earth-reduced precursors and permanent magnet manufacturing, respectively. As a result, they suppressed the formation of unnecessary magnetic particles inside the magnet and optimized its microstructure. This simultaneously improved the magnet’s key properties of remanence and coercivity. The domestic market size for rare earth permanent magnets for high-efficiency motors reached 186 billion KRW annually as of 2021, but almost all are imported. This technology can be applied to electric vehicles, drones, flying cars, and electric ships.

Kim Taehoon, principal researcher at the Materials Institute, said, "Among materials that determine motor performance, permanent magnets have the greatest impact, and the stronger the magnet, the better the performance." He added, "South Korea recognized the issue of China’s rare earth supply monopoly only in the late 2000s and started researching domestic rare earth permanent magnet technology somewhat late." He continued, "Even if technology is developed at the laboratory level, it often fails to work properly at mass production stages. To efficiently develop technology and raise the overall industrial level, policy support is needed to enable research institutions to study mass production technologies as well."