A
magnetic domain is a region within a magnetic material in which the magnetization is in a uniform direction. This means that the individual
magnetic moments of the atoms are aligned with one another and they point in the same direction. When cooled below a temperature called the
Curie temperature, the magnetization of a piece of
ferromagnetic material spontaneously divides into many small regions called magnetic domains. The magnetization within each domain points in a uniform direction, but the magnetization of different domains may point in different directions. Magnetic domain structure is responsible for the magnetic behavior of
ferromagnetic materials like
iron,
nickel,
cobalt and their
alloys, and
ferrimagnetic materials like
ferrite. This includes the formation of
permanent magnets and the attraction of ferromagnetic materials to a magnetic field. The regions separating magnetic domains are called
domain walls, where the magnetization rotates coherently from the direction in one domain to that in the next domain. The study of magnetic domains is called
micromagnetics.