The property [altermagnetism] could boost the storage on computer hard drives, because commercial devices contain ferromagnetic material that is so tightly packed that the material’s external magnetic fields start to see interference – altermagnets could be packed more densely.
I’m not clear on how such a drive would work. Aren’t the material’s external magnetic fields necessary in order to be able to “read” the data?
I’m guessing they’re handwaving away bit detection as a problem to solve later. That’s not unreasonable for basic research purposes, really; you could imagine other ways of reading the spin of atoms might be possible.
The original research cited is written in a pretty inaccessible way, so I can’t really comment on the usefulness as a store of information yet.