  We show that 2D and 3D electron systems with the long-range Coulomb
electron-electron interaction could develop ferromagnetic instabilities due to
strong exchange effects at low densities. The critical densities in both 2D and
3D systems at which the magnetic instability, which could either be of Stoner
type (second-order) or of Bloch type (first-order), are higher than the
dispersion instability critical density where effective mass at the Fermi
surface diverges. We discuss the theoretical as well as experimental
implications of the ferromagnetic instability at low electron densities,
particularly in low-disorder semiconductor-based two-dimensional systems.
