Today I spent some time looking more closely at Mn-Fe-Si as a chemistry possibly worth exploring. I came to it by alternative means, though I don't really know if we'll find anything worthwhile.
I generated a few different materials, looking for candidates with decent Curie and Ms. Of course stability is a prerequisite.
It looks like a fairly stable chemistry.
Phase diagram of MnFe6Si; e_above_hull: 0.041436 eV/atom; predicted_stable: False
As you can see from the generated phase diagram, there are a handful of structures with this chemistry already catalogued on Materials Project.
Of these, MnFe6Si was interesting and worth further study. Quite stable (seen above), and good properties I've tested so far. MAE was low, as has everything else we've looked at but it could be a good candidate for doping with Sulfur.
MnFe6Si (space group: P4/mmm #123, crystal system: tetragonal, point group: 4/mmm)
I'm still working on a doping study to see what kind of MAE improvements we can make. I need to focus on that completely, assuming it is true and that doping will be required. Will's tree search will continue to search for pure bulk materials.
Perhaps I'm more skeptical we'll find a pure bulk material with everything we need, given we haven't found anything close just yet.
Is it a matter of:
it doesn't exist
haven't searched enough in existing chemistries
our models are bad and not able to discriminate properly
haven't come across the right chemistry yet
or something else
Going to do more of these stream-of-consciousness type posts for others to get a look inside of the work that is going on daily towards the goal of discovering an ideal rare-earth-free permanent magnet. Stay tuned.