[Animats]

Yup. Here's that startup: https://www.nironmagnetics.com

Lots of green eco verbiage and mentions of funders. No products, no samples.

Researchers have been beating on this problem since at least 2003.[1] Someone may crack this problem, but the hype to results ratio is large here.

Rare earths aren't really scarce. There's a boom and bust cycle.

Recent history: Biggest producer was in California. Low-cost rare earths from China resulted in shutdown of Mountain Pass CA mine. Prices raised by China producers. Major freak out in magnet industry. Mountain Pass mine restarted. China drops prices. Rare earth glut around 2015. Mountain Pass mine shut down again. Rare earth supply looking uncertain and rare earths demand increases. Mountain Pass mine started up again. Rare earth mines starting up in Australia. Processing plant in US starts up this quarter. More processing plants being built in US, Canada, Australia. Major auto industry customers now making long term deals with suppliers to get some stability. Push by DoD to get secure US supply.

[1] https://ieeexplore.ieee.org/document/8508460

[rfoo]

So rare earths are the DRAM of manufacturing industry?

[Turing_Machine]

It's not just rare earths... lots of minerals (most glamorously, gold) are this way. There are mines that are profitable to operate if the mineral is selling for $x per kilogram (or gram, or tonne), but are not profitable to operate if it's selling for $x-1 per unit (or any other figure less than x). Shutting mines down and (sometimes) starting them back up based on economic reasons has been going on for centuries.