  Recent advances in high-density magnetic storage and spin electronics are
based on the use of magnetic materials along with conventional microelectronic
materials (metals, insulators and semiconductors). The unit information (bit)
is stored as a magnetization state in some ferromagnetic ma rial (FM) and
controlled with an external field altering the magnetization state. As device
size is shrinking steadily toward the nanometer and the need to incr se its
bandwidth prevails, racing toward higher frequencies is getting even more cha
enging. In magnetic systems, denser storage leads to finer magnetic grains and
small size leads to single magnetic domain physics. The Stoner-Wohlfarth model
is the simplest model that describes adequately the physics of fine magnetic
grains containing single domains and where magnetization state changes by
rotation or switching (abrupt reversal). The SW model is reviewed and discussed
with its consequences and potential app cations in the physics of magnetism and
spin electronics.
