The study of magnetic materials and magnetic devices at nanometre or atomic scale. The material systems mainly include magnetic ultrathin films with a thickness of a few nanometres, magnetic wires with a width of less than 100 nm, and magnetic dots with a diameter of less than 100 nm. Due to reduced dimension in these magnetic nanostructures, the magnetic anisotropy, magnetoresistance, and magnetization reversal are distinctively different from their bulk materials. Nanomagnetism is investigated both to understand the new phenomena and to explore the novel properties in nanoscale materials and devices for such industrial applications as magnetic data storage and nanotechnology.