The spin magnetic moment is the fundamental source of magnetism at the atomic level, arising from the intrinsic angular momentum of electrons. Unlike the orbital magnetic moment caused by an electron moving around a nucleus, this moment comes from the electron acting like a tiny spinning charge. In ferromagnetic materials like iron, these individual moments align in domains to produce a strong, macroscopic magnetic field.
Heard on the job
The rare-earth magnets in the new SPM motor get their high flux density primarily from the aligned spin magnetic moments of the unpaired electrons.