What Is Tesla’s Mystery Magnet?

Tesla’s investor day on 1 March started with a rambling, detailed discourse on power and the surroundings earlier than transitioning right into a sequence of principally predictable bulletins and boasts. And then, out of nowhere, got here an absolute bombshell: “We have designed our next drive unit, which uses a permanent-magnet motor, to not use any rare-earth elements at all,” declared Colin Campbell, Tesla’s director of power-train engineering.

It was a surprising disclosure that left most consultants in everlasting magnetism cautious and perplexed. Alexander Gabay, a researcher on the University of Delaware, states flatly: “I am skeptical that any non-rare-earth permanent magnet could be used in a synchronous traction motor in the near future.” And at Uppsala University, in Sweden, Alena Vishina, a physicist, elaborates, “I’m not sure it’s possible to use only rare-earth-free materials to make a powerful and efficient motor.”

The downside right here is physics, which not even Tesla can alter.

And at a current magnetics convention Ping Liu, a professor on the University of Texas, in Arlington, requested different researchers what they considered Tesla’s announcement. “No one fully understands this,” he stories. (Tesla didn’t reply to an e-mail asking for elaboration of Campbell’s remark.)

Tesla’s technical prowess ought to by no means be underestimated. But then again, the corporate—and particularly, its CEO—has a historical past of creating sporadic sensational claims that don’t pan out (we’re nonetheless ready for that US $35,000 Model 3, for instance).

The downside right here is physics, which not even Tesla can alter. Permanent magnetism happens in sure crystalline supplies when the spins of electrons of a few of the atoms within the crystal are compelled to level in the identical route. The extra of those aligned spins, the stronger the magnetism. For this, the perfect atoms are ones which have unpaired electrons swarming across the nucleus in what are often called 3d orbitals. Tops are iron, with 4 unpaired 3d electrons, and cobalt, with three.

But 3d electrons alone aren’t sufficient to make superstrong magnets. As researchers found many years in the past, magnetic energy will be enormously improved by including to the crystalline lattice atoms with unpaired electrons within the 4f orbital—notably the rare-earth parts neodymium, samarium, and dysprosium. These 4f electrons improve a attribute of the crystalline lattice known as magnetic anisotropy—in impact, they promote adherence of the magnetic moments of the atoms to the precise instructions within the crystal lattice. That, in flip, will be exploited to realize excessive coercivity, the important property that lets a everlasting magnet keep magnetized. Also, via a number of complicated bodily mechanisms, the unpaired 4f electrons can amplify the magnetism of the crystal by coordinating and stabilizing the spin alignment of the 3d electrons within the lattice.

Since the Eighties, a everlasting magnet based mostly on a compound of neodymium, iron, and boron (NdFeB), has dominated high-performance purposes, together with motors, smartphones, loudspeakers, and wind-turbine turbines. A 2019 examine by Roskill Information Services, in London, discovered that greater than 90 % of the everlasting magnets utilized in automotive traction motors had been NdFeB.

So if not rare-earth everlasting magnets for Tesla’s subsequent motor, then what form? Among consultants keen to invest, the selection was unanimous: ferrite magnets. Among the non-rare-earth everlasting magnets invented up to now, solely two are in large-scale manufacturing: ferrites and one other kind known as Alnico (aluminum nickel cobalt). Tesla isn’t going to make use of Alnico, a half-dozen consultants contacted by IEEESpectrum insisted. These magnets are weak and, extra vital, the world provide of cobalt is so fraught that they make up lower than 2 % of the permanent-magnet market.

There are greater than a rating of everlasting magnets that use no rare-earth parts, or don’t use a lot of them. But none of those have made an influence outdoors the laboratory.

Ferrite magnets, based mostly on a type of iron oxide, are low cost and account for almost 30 % of the permanent-magnet market by gross sales. But they, too, are weak (one main use is holding fridge doorways shut). A key efficiency indicator of a everlasting magnet is its most power product, measured in megagauss-oersteds (MGOe). It displays each the energy of a magnet in addition to its coercivity. For the kind of NdFeB generally utilized in automotive traction motors, this worth is usually round 35 MGOe. For the very best ferrite magnets, it’s round 4.

“Even if you get the best-performance ferrite magnet, you will have performance about five to 10 times below neodymium-iron-boron,” says Daniel Salazar Jaramillo, a magnetics researcher on the Basque Center for Materials, Applications, and Nanostructures, in Spain. So in comparison with a synchronous motor constructed with NdFeB magnets, one based mostly on ferrite magnets shall be a lot bigger and heavier, a lot weaker, or some mixture of the 2.

To ensure, there are greater than a rating of different everlasting magnets that use no rare-earth parts or don’t use a lot of them. But none of those have made an influence outdoors the laboratory. The checklist of attributes wanted for a commercially profitable everlasting magnet contains excessive area energy, excessive coercivity, tolerance of excessive temperatures, good mechanical energy, ease of producing, and lack of reliance on parts which are scarce, poisonous, or problematic for another motive. All of the candidates in the present day fail to tick a number of of those bins.

Iron-nitride magnets, reminiscent of this one from startup Niron Magnetics, are among the many most promising of an rising crop of everlasting magnets that don’t use rare-earth parts.Niron Magnetics

But give it just a few extra years, say some researchers, and one or two of those may very properly break via. Among probably the most promising: iron nitride, Fe₁₆N₂. A Minneapolis startup, Niron Magnetics, is now commercializing expertise that was pioneered with funding from ARPA-E by Jian Ping Wang on the University of Minnesota within the early 2000s, after earlier work at Hitachi. Niron’s govt vp, Andy Blackburn, informed Spectrum that the corporate intends to introduce its first product late in 2024. Blackburn says it will likely be a everlasting magnet with an power product above 10 MGOe, for which he anticipates purposes in loudspeakers and sensors, amongst others. If it succeeds, it will likely be the primary new business everlasting magnet since NdFeB, 40 years in the past, and the primary business non-rare-earth everlasting magnet since strontium ferrite, the very best ferrite kind, 60 years in the past.

Niron’s first providing shall be adopted in 2025 by a magnet with an power product above 30 MGOe, in line with Blackburn. For this he makes a reasonably daring prediction: “It’ll have as good or better flux than neodymium. It’ll have the coercivity of a ferrite, and it’ll have the temperature coefficients of samarium cobalt”—higher than NdFeB. If the magnet actually manages to mix all these attributes (an enormous if), it could be very properly fitted to use within the traction motors of electrical autos.

There shall be extra to come back, Blackburn declares. “All these new nanoscale-engineering capabilities have allowed us to create materials that would have been impossible to make 20 years ago,” he says.