Permanent magnets

2025: Scientists offer affordable alternative to rare earth magnets

Scientists have proposed an affordable alternative to rare earth magnets. NITU MISIS announced this on March 11, 2025.

With the help of this technology, Russian scientists have obtained material for the manufacture of more stable permanent magnets that can replace expensive analogues with rare earth elements. The development is promising for use in electronics, audio and household appliances, as well as in the automotive industry and industry.

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Фото: MISIS

Permanent magnets are used in electronics, medical equipment, sensors, generators, motor control systems, various automation mechanisms, for packaging and holding metal parts. Depending on the purpose, magnets are most often made of neodymium-iron-boron alloy or barium or strontium hexagonal ferrites. Neodymium magnets are the most powerful, but ferrite magnets are much cheaper, more affordable and more resistant to chemical influences and corrosion. As of March 2025, the urgent task is to improve the characteristics of ferrite magnets in order to replace neodymium magnets with them.

Researchers of NUST MISIS and the Institute of General and Inorganic Chemistry. N.S. Kurnakov RAS offered their alternative to expensive rare earth magnets. First, they obtained a powder from disk-shaped barium hexaferrite nanoplates, which has a high coercive force - the magnitude of the external magnetic field strength necessary to re-magnetize the substance.

On average, the coercive strength of commercially available and used brands of barium ferrites is up to 4 kE, less often - 5 kE. The powder we have obtained has a coercive force of 5.6 kE, thanks to which it surpasses most of the known analogues, - said Candidate of Technical Sciences Andrei Timofeev, Associate Professor of the Department of Electronics Materials Technology at NITU MISIS.

To obtain a magnet, the powder must be sintered - subjected to a high-temperature treatment (1100-1300 ° C) to form a bulk ceramic product. In this case, the particles begin to grow together, and their size increases, which leads to a decrease in coercive force. To solve this problem, the researchers applied liquid-phase sintering technology, in which ferrite powder is pre-mixed with a low-melting additive. When heated, it becomes liquid and fills the pores between the solid particles, facilitating their redistribution and compaction. After cooling, the liquid phase solidifies to form a dense and strong material.

The researchers added different amounts of bismuth oxide or boron oxide to the ferrite particles, and then the resulting mixture was molded and sintered at 900 ° C. Despite some growth in particle size, strong ceramic samples were obtained that retained a coercive force at a high level - 5.3 kE.

Scientists have long been trying to improve the magnetic characteristics of hexaferrites using various methods. The uniqueness of our development in combining several technologies. The first is the preparation of hexaferrite nanoplates of a certain shape, which requires special conditions for synthesis. The second is low-temperature sintering, with the help of which ceramics are obtained with the preservation of magnetic parameters of the initial powder. This material can be used in the future to create more efficient ferrite magnets, "said Andrey Mironovich, Ph.D., Associate Professor, Department of Electronics Materials Technology, NITU MISIS.