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Rare-earth-free permanent magnet candidate system. WIP.
As we'll see below, Fe-N want to form with high N concentrations. No surprises there. The midpoint FeN compound is so low energy that it takes a lot off the hull, basically leaving a void around it. Pretty interesting. Since I've never seen this, I want to confirm this is correct and not some artifact of a bad energy or something.
This phase diagram is interesting. While we searched all over Fe-N, it's very clear that mostly only low concentrations of nitrogen are stable (not surprising!). Though, there is FeN but this is an outlier. It's interesting how low energy it is. Materials Project PD showed the same thing.
It's not the most stable, but it's the best tetragonal Fe-N compound I've found so far. I got to fix the naming or parsing of these, because for some reason the file shows Fe4N2 but it's actually just Fe2N I believe. I'd prefer to leave as full stoichiometry not reduced formula consistently.
74 meV above the hull
This thing cooked. This could be similar to what the Niron guys are after, although their formula is Fe16N2.
Magnetic density: 0.118
MAE: 3.653
This one had a space group I've never seen but I knew was some kind of tetragonal. Magnetic density is better than Fe4N2 with the greater iron concentration.
Never seen this space group before
MAE: 0.4524
An unfortunate letdown!