WhereIsAtlas · Materials science
What Happened to Rare Earth Magnets?
They were discovered in an Air Force lab, then invented twice in the same year by GM and a Japanese rival. Now nearly all of them are made in one country.
Rare earth magnets are the strongest permanent magnets known. Samarium-cobalt came first in 1966 from US Air Force research; neodymium-iron-boron was invented independently in 1983 by teams at General Motors and Sumitomo Special Metals. The technology is thriving — but its manufacture has concentrated almost entirely in China.
A story that starts in a Swedish quarry
The rare earth elements were not discovered all at once. The first rare earth mineral was described in 1751 by the Swedish chemist Axel Fredrik Cronstedt. The real chemistry began in 1787, when Carl Axel Arrhenius found a dense black mineral near Ytterby in Sweden; Johan Gadolin analysed it in 1794 and identified a new "earth", which became known as yttria. A second earth, ceria, was isolated in 1803.
Separating the individual elements took another century. Most were resolved during the late 19th and early 20th centuries, and samarium — the element that would eventually make the first practical rare earth magnet — was identified spectroscopically in 1879 by Paul-Émile Lecoq de Boisbaudran in the mineral samarskite.
Four of the elements are named after that one Swedish village. It is not a coincidence: Ytterby is where the chemistry started.
The Air Force lab and the first rare earth magnet
The first generation of rare earth permanent magnets was samarium-cobalt, developed in the 1960s and early 1970s. The foundational breakthrough came from Karl J. Strnat and colleagues at the U.S. Air Force Materials Laboratory, who in 1966 found exceptionally high magnetocrystalline anisotropy in rare earth-cobalt alloys.
The result was SmCo₅, and its practical significance was immediate: it tripled the energy product of the Alnico magnets then in use. A second generation, Sm₂Co₁₇, arrived in the 1970s with even greater magnetic strength. Rare earths had gone from a chemistry curiosity to the best permanent magnets anyone had ever made.
1983: invented twice, in two countries
Then came the leap. Neodymium-iron-boron — NdFeB — is the strongest permanent magnet in commercial use, and it was invented independently in 1983 by two teams who were not working together and did not know about each other's results.
One team was led by John J. Croat at General Motors in the United States. The other was led by Masato Sagawa at Sumitomo Special Metals in Japan. Both announced their work at the same conference in Pittsburgh that year — one of the cleanest examples of simultaneous invention in industrial history.
Two companies, two routes
The two inventions were not identical, and the difference shaped an industry. General Motors commercialised its technology through its Magnequench division, which concentrated on bonded and hot-pressed NdFeB magnets; GM spun the division out in 1995.
Sumitomo Special Metals took the other path, developing the sintered process and securing the dominant patent position. That business later became part of Hitachi Metals, which remains a major producer of sintered NdFeB and has been involved in patent litigation and in expanding production in the United States.
Sintered magnets became the route for the strongest applications — traction motors, wind turbines — while bonded magnets filled smaller, cheaper roles. The patent position mattered enormously for two decades, and its expiry reshaped who could make what.
Why this matters far beyond materials science
Rare earth magnets are not a niche component. They are inside electric vehicle motors, the generators of wind turbines, headphones and speakers, hard drives, and a long list of defence systems. Any technology that needs high magnetic strength in a small space depends on them.
That makes the supply chain a strategic question rather than an industrial one. And the chain is unusually concentrated: China dominates not just rare earth mining but the separation chemistry and the magnet manufacturing that follow, while Western raw material has largely come from a single mine at Mountain Pass, California.
Where rare earth magnets are now
The technology is not in decline — it is expanding, because electrification and renewable energy both run on strong magnets. NdFeB remains the strongest commercially available type, with samarium-cobalt still preferred where high-temperature stability matters more than raw strength.
What has changed is the politics of making them. Governments now treat magnet supply as critical infrastructure, and the West is trying to rebuild separation and magnet production outside China. The magnets themselves were a triumph of open industrial research. The problem that followed is that almost all of the factories ended up in one place.
Frequently asked questions
These are the questions people actually search for about rare earth magnets, answered directly.
What is the strongest permanent magnet?
Neodymium-iron-boron (NdFeB), invented in 1983.
Who invented neodymium magnets?
Two teams independently: John J. Croat at General Motors and Masato Sagawa at Sumitomo Special Metals, both in 1983, both announced at the same Pittsburgh conference.
What is the difference between samarium-cobalt and neodymium magnets?
Samarium-cobalt came first (1966) and handles high temperatures better; neodymium-iron-boron is stronger but more sensitive to heat. Both are rare earth magnets.
Are rare earth magnets actually rare?
The elements are not geologically rare — several are more abundant than copper. The difficulty is separating them economically and processing them cleanly, which is why usable supply is concentrated.
Why are rare earth magnets a national security issue?
Because they are essential to EV motors, wind turbines and defence systems, and almost all mining, separation and magnet manufacturing is concentrated in China.
Entries in this story
Sources
- The men who made the magnet that made the modern world — IEEE Spectrum (2026-09-15)
- John J. Croat — biography and NdFeB work at General Motors — Engineering and Technology History Wiki (ETHW) (2026-09-15)
- A technical guide to the discovery and enduring legacy of samarium-cobalt rare-earth magnets — BenchChem (2026-09-15)
- SmCo magnets — technical data sheet — Quadrant (2026-09-15)
- Rare earth mining may be key to our renewable energy future — but at what cost? — Ames National Laboratory (Science News) (2026-09-15)
- Mountain Pass history and timeline — MP Materials (2026-09-15)