“Tesla’s mystery magnet” is the undisclosed material in a rare-earth-free permanent-magnet drive unit Tesla said it had designed. At its 1 March 2023 Investor Day, Tesla powertrain engineering leader Colin Campbell announced the design but did not identify the magnet chemistry. Ferrite was the leading expert hypothesis reported by IEEE Spectrum—not a Tesla confirmation. Iron nitride is another rare-earth-free possibility in the wider industry, but no cited source connects it to Tesla.
What did Tesla actually announce?
At Tesla’s Investor Day on 1 March 2023, Colin Campbell, who introduced himself as leading Tesla powertrain engineering, said: “We have designed our next drive unit, which uses a permanent magnet motor to not use any rare earth materials at all.” Tesla’s Investor Day 2023 Keynote is the primary source for that statement.
The wording establishes a design claim: a next drive unit with a permanent-magnet motor that avoids rare-earth materials. It does not name the magnet material or a supplier, provide a detailed specification, or establish that the design entered production. IEEE Spectrum reported that Tesla did not elaborate in response to its request for comment.
Why does the magnet material matter?
A permanent magnet’s performance depends on how strongly it can magnetize and how well it resists losing that magnetization, a property called coercivity. Rare-earth elements help provide the magnetic anisotropy needed for strong performance. Neodymium-iron-boron (NdFeB) magnets have been widely used in high-performance motor applications, including automotive traction motors.
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IEEE Spectrum reported that a 2019 Roskill Information Services study found NdFeB accounted for more than 90 percent of permanent magnets used in automotive traction motors. That is a historical figure attributed to the 2019 study, not a current market estimate.
For scale, IEEE Spectrum reported approximate maximum energy products of around 35 MGOe for the NdFeB type commonly used in automotive traction motors and around 4 MGOe for the best ferrite magnets. MGOe means megagauss-oersteds; maximum energy product is an indicator of magnetic strength and coercivity. These approximate values are not universal for every grade, and the metric alone does not determine how a complete motor performs.
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Is Tesla’s magnet ferrite?
That has not been confirmed. IEEE Spectrum asked magnetism experts to speculate, and ferrite was their leading guess. Ferrite magnets are iron-oxide-based, contain no rare-earth elements, are inexpensive, and are an established material family. Those attributes make ferrite a plausible candidate to discuss, but they do not show Tesla selected it.
The main tradeoff is performance. IEEE Spectrum quoted magnetics researcher Daniel Salazar Jaramillo of the Basque Center for Materials, Applications, and Nanostructures saying that even the best-performing ferrite would have performance “about five to 10 times below neodymium-iron-boron.” A motor designed around ferrite could require a larger or heavier magnet arrangement, deliver less strength, or combine those compromises. That is a design challenge, not proof that ferrite cannot work in a traction motor.
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Alnico is another established permanent-magnet family without rare earths. Experts interviewed by IEEE Spectrum considered it unlikely for this application, citing comparatively weak magnets and cobalt-supply concerns. This was expert opinion, not a Tesla decision.
What about iron nitride?
Iron nitride, including the Fe16N2 composition discussed by IEEE Spectrum, is an emerging rare-earth-free magnet candidate. It should not be confused with a disclosed Tesla material: the sources cited here do not connect iron nitride or its developer, Niron Magnetics, to Tesla’s drive-unit design.
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Niron says it is commercializing iron-nitride permanent magnets. Its current homepage says it is “actively manufacturing and sampling customers from its commercial pilot plant today.” That is the company’s account of its development and sampling status, not independent verification of automotive-scale performance or evidence of a Tesla supply relationship. The U.S. Department of Energy also described Niron pilot production for commercial sampling in a notice dated 19 January 2023.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.How the candidate materials compare
| Material family | What is established | Important qualification |
|---|---|---|
| NdFeB | Established high-performance permanent-magnet family; widely used in motor applications. | Contains rare-earth elements. IEEE Spectrum’s approximate 35 MGOe comparison refers to the type commonly used in automotive traction motors. |
| Ferrite | Established, inexpensive, rare-earth-free magnet family; leading expert hypothesis reported for Tesla’s design. | Tesla has not confirmed it. IEEE Spectrum reported around 4 MGOe for the best ferrite magnets, substantially below its automotive NdFeB comparison. |
| Alnico | Established permanent-magnet family that does not use rare earths. | Experts quoted by IEEE Spectrum considered it unlikely for this traction-motor use; this is not a Tesla statement. |
| Iron nitride | Emerging rare-earth-free family; Niron reports commercial-pilot manufacturing and customer sampling. | No cited source ties it to Tesla. Niron’s status is company-reported, not proof of automotive-scale performance. |
A motor designer must weigh more than maximum energy product: coercivity, temperature tolerance, mechanical robustness, manufacturability, material supply, and the resulting motor’s size, mass, and output all matter. Without a Tesla specification and application details, these families cannot be ranked as if one number settled the choice.
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What remains unknown?
- The chemistry of the magnet in Tesla’s announced design.
- Whether Tesla’s announced unit entered production, and in what implementation.
- Whether any emerging magnet company supplies or will supply Tesla.
Until Tesla provides authoritative details, the accurate answer is that the material remains undisclosed. The source for the announcement is Tesla’s Investor Day 2023 Keynote; the candidate-material analysis and attributed performance comparisons come from IEEE Spectrum’s March 2023 article. Niron’s current commercialization description appears on its company overview and homepage; the historical pilot-production notice is from the U.S. Department of Energy, 19 January 2023.
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