Last month, at a livestreamed Tesla investor event that went short on new cars and long on grandiose narratives, a minor detail in Elon Musk’s “Master Plan Part 3” made big news in an obscure corner of physics. Colin Campbell, an executive in Tesla’s powertrain division, announced that his team was expunging rare-earth magnets from its motors, citing supply chain concerns and the toxicity of producing them.
To emphasize the point, Campbell clicked between a pair of slides referring to three mystery materials, helpfully labeled Rare Earths 1, 2, and 3. On the first slide, representing Tesla’s present, the amounts range from a half kilo to 10 grams. On the next—the Tesla of an unspecified future date—all were set to zero.
To magneticians, folks who study the uncanny forces some materials exert thanks to the movements of electrons and sometimes use cryptic hand gestures, the identity of Rare Earth 1 was obvious: neodymium. When added to more familiar elements, like iron and boron, the metal can help create a powerful, always-on magnetic field. But few materials have this quality. And even fewer generate a field that is strong enough to move a 4,500-pound Tesla—and lots of other things, from industrial robots to fighter jets. If Tesla planned to eliminate neodymium and other rare earths from its motors, what sort of magnets would it use instead?
One thing was clear to the physicists: Tesla had not invented a fundamentally new magnet material. “You get a new commercial magnet a couple times a century,” says Andy Blackburn, EVP of strategy of Niron Magnetics, one of the few startups trying to notch up the next such revelation.
More likely, Blackburn and other flux heads figured, was that Tesla had decided it can make do with a much less powerful magnet. The obvious candidate from the short list of possibilities, most of which include expensive and geopolitically fraught elements like cobalt, was ferrite: a ceramic of iron and oxygen, mixed with a bit of a metal such as strontium. It’s cheap and easy to make, and has kept refrigerator doors everywhere stuck shut since the 1950s.
But ferrite also packs only about one-tenth the magnetic punch as neodymium magnets, by volume, which raises new questions. Tesla CEO Elon Musk is known for being uncompromising, but if Tesla is switching to ferrite, it appeared that something's got to give. (The company did not respond to a request for comment.)
It’s tempting to think the battery is what makes an EV go, but really it’s electromagnetism that moves an electric car. (It’s no coincidence that Tesla, the company, and tesla, the unit of magnetism, are named after the same guy.) When electrons flow through coils of wire in the motor, they create an electromagnetic field that pushes against opposing magnetic forces, rotating the motor’s shaft and causing the wheels to spin.
For the rear wheels of a Tesla, those forces are provided by a motor with permanent magnets, materials with the strange property of having a steady magnetic field, without any electrical input, thanks to the well-orchestrated spin of electrons around its atoms. Tesla only started adding these magnets to its cars about five years ago to eke out more miles and boost torque without upgrading the battery. Before that it used induction motors built around electromagnets, which become magnetic by consuming electric current. (Those are still in use in models that have front motors.)
That might make getting rid of rare earths and forswearing the best magnets around seem a little weird. Car companies typically obsess over efficiency—especially in the case of EVs, where the fight remains on to convince drivers to get over their fears about limited range. But as automakers start to scale up EV production, some engineering previously considered too inefficient is making a comeback.
That’s seen in automakers—Tesla among them—producing more vehicles with batteries made with LFP, lithium iron phosphate. These tend to be lower-range models than those with batteries that contain elements like cobalt and nickel. It’s older technology. Heavier? Sure. Packs less energy, too. (The current LFP-powered Model 3 promises 272 miles of range, while a long-range Model S with a fancier battery can top 400.) But it can be a smarter business choice because it avoids dealing with expensive and politically dicey materials.
Still, it’s unlikely that Tesla is simply replacing its magnets with something far worse, like ferrite, without making other changes. “You’ll have a huge magnet to carry around in a car,” says Alena Vishina, a physicist at Uppsala University. Luckily, a motor is a fairly complex machine with plenty of other components that, in theory, can be rearranged to soften the penalty of using weaker magnets. In computer models, materials company Proterial recently determined that by carefully positioning ferrite magnets and tweaking other aspects of motor design, many performance metrics of rare-earth-driven motors can be replicated. The result in that case was a motor that’s only about 30 percent heavier, a difference that could be small relative to a car's overall bulk.
Despite such headaches, there are plenty of reasons for a car company to get rid of rare earth elements, if they can swing it. Ever since the early 1990s, when China’s leader, Deng Xiaoping, declared the metals to be his country’s equivalent to Saudi oil, they’ve been a kind of buzzword for trans-Pacific geopolitical anxieties. Never mind that rare earths are nothing like oil—the total market is worth about the same as the US egg market, and the elements can theoretically be mined, processed, and turned into magnets all over the world. But China is the only place that does all of it.
China’s near-monopoly is partly due to economics—in the 1990s, cheap Chinese rare earths flooded the market, hastening the shutdown of mines and processing in places like the US—and partly due to environmental concerns. Mining and refining rare earths is a notoriously toxic business, in part because the most valuable elements, like that magnet-boosting neodymium, come tightly bound with other rare earths, as well as radioactive elements like uranium and thorium. Today, China produces nearly two-thirds of rare earths mined worldwide and processes more than 90 percent of the world’s magnets.
“You have a $10 billion industry, which enables products that are worth between $2 trillion and 3 trillion a year. It’s enormous leverage,” says Thomas Kruemmer, a minerals analyst and author of the popular Rare Earth Observer blog. That’s true for cars too, he says—even if they contain just a few kilograms of the stuff. Taking them out means the car won’t go (unless you’re willing to redesign the whole motor).
The US and Europe are trying to diversify that supply chain. A California mine that closed in the early 2000s recently reopened and now supplies 15 percent of the world’s rare earths—though that ore is shipped to China for processing. In the US, government agencies—especially the Department of Defense, which needs powerful magnets for gear including aircraft and satellites—have been keen to invest in supply chains domestically and in friendly places like Japan and Europe. (The Department of Energy, meanwhile, is looking at how to use seaweed to sequester rare earths from seawater.) But it’s slow going—years, or even decades in the making, given the costs, know-how needed, and environmental issues.
Meanwhile, demand is rising for magnets embedded in the tools of decarbonization, such as cars and wind turbines. Currently, 12 percent of rare earths go into EVs, according to Adamas Intelligence, a market that’s just now taking off. At the same time, rare earth prices have recently whiplashed due to internal Chinese markets and political interventions that outside companies cannot always predict.
All in all, if you’re in a business where you can make an alternative work, it probably makes sense to do so, says Jim Chelikowsky, a physicist who studies magnetic materials at the University of Texas, Austin. But there are all kinds of reasons, he says, to look for better alternatives to rare earth magnets than ferrite. The challenge is finding materials with three essential qualities: They need to be magnetic, to hold that magnetism in the presence of other magnetic fields, and to tolerate high temperatures. Hot magnets cease to be magnets.
Researchers have a pretty good sense of what chemical elements can make good magnets, but there are millions of potential atomic arrangements. Some magnet hunters have taken the approach of starting with hundreds of thousands of possible materials, tossing out those with drawbacks like containing rare earths, and then using machine learning to predict the magnetic qualities of those that remain. Late last year, Chelikowsky published results from using the system to create a new highly magnetic material containing cobalt. That’s not ideal, geopolitically speaking, but it’s a starting point, he says.
Often the greatest challenge is finding new magnets that are easy to make. Some newly developed magnets, such as those containing manganese, are promising, Vishina at Uppsala University explains, but also unstable. In other cases, scientists know that a material is extraordinarily magnetic but can’t be create in bulk. That includes tetrataenite, a nickel-iron compound known only from meteorites that must slowly cool over thousands of years to precisely arrange its atoms into the correct state. Attempts to make it more speedily in the lab are ongoing but have yet to bear fruit.
Niron, the magnet startup, is a little further along, with an iron nitride magnet that the company says is theoretically more magnetic than neodymium. But it too is a fickle material, hard to make and preserve in a desirable form. Blackburn says the company is making progress but won’t be producing magnets powerful enough to transform EVs in time for Tesla’s next generation of vehicles. First step, he says, is to put the new magnets in smaller devices like sound systems.
It’s unclear whether other automakers will follow Tesla’s rare earth trade-off, Kruemmer says. Some might stick with the baggage-laden materials, while others go with induction motors or try something new. Even Tesla, he says, probably will have a few grams of rare earths sprinkled in its future vehicles, spread across things like the automatic windows, power steering, and windshield wipers. (In a possible sleight of hand, the slides contrasting rare earth content at Tesla’s investor event actually compared an entire current-generation car to a future motor.) Despite workarounds like those in the works at Tesla, rare earth magnets sourced from China will remain with us—including Elon Musk—especially as the world pushes to decarbonize. It might be nice to replace everything, but as Kruemmer says, “we simply do not have the time.”
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Tracy Wen Liu
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