From Applied Science.

I show the process of making iron nitride permanent magnets by ball milling ammonium nitrate and iron powder. Some researchers think that the theoretical performance limit of iron nitride magnets is higher than neodymium iron boron, but so far, no one has been able to show this.

Main paper that I used: https://sci-hub.se/http://dx.doi.org/10.1002/adem.201500455
https://www.connectedpapers.com/main/d9bb02f3a85d6f74be490b1504435b87403ab191/Preparation-of-an-%CE%B1%E2%80%B3%E2%80%90Fe16N2-Magnet-via-a-Ball-Milling-and-Shock-Compaction-Approach-%E2%80%89/graph

Company working on commercializing iron nitride: https://www.nironmagnetics.com/

More references:
https://sci-hub.ru/https://doi.org/10.1016/j.jmmm.2019.165962
https://conservancy.umn.edu/items/5ba0e697-ff69-42e6-9773-4b1dc965c604
https://sci-hub.se/https://doi.org/10.1016/j.progsolidstchem.2017.06.001
https://www.lakeshore.com/docs/default-source/product-downloads/application-notes/permanent-magnet-paper.pdf?sfvrsn=1ccd61c7_1
https://par.nsf.gov/servlets/purl/10203577
https://sci-hub.ru/https://doi.org/10.1063/1.5017708

Planetary ball mill plans and materials list: https://github.com/benkrasnow/Planetary_Ball_Mill

Alumitone pickup: https://lacemusic.com/products/alumitone-humbucker

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