Magnetic domains are regions within a magnetic material where the magnetic moments of atoms are uniformly aligned in the same direction. Each domain acts like a tiny magnet with its own magnetization direction
. In ferromagnetic materials such as iron, nickel, and cobalt, these domains form spontaneously below a certain temperature (the Curie temperature) to minimize the material's internal energy. Instead of having a uniform magnetization throughout the entire material, the material divides into many small domains with different magnetization directions. This arrangement reduces the external magnetic field and thus lowers the magnetostatic energy
. The boundaries between these regions are called domain walls, where the magnetization gradually changes direction from one domain to another. The size and structure of domains result from a balance between the energy saved by reducing the external field and the energy cost of creating domain walls
. When an external magnetic field is applied, the domains tend to align with the field, causing the material to become magnetized. If the alignment persists after removing the external field, the material becomes a permanent magnet. This behavior is related to hysteresis in magnetic materials
. In summary, magnetic domains are microscopic areas inside ferromagnetic materials where atomic magnetic moments align uniformly, and their collective behavior determines the magnetic properties of the material
