Weiss domains are small areas in a crystal structure of a ferromagnetic material with uniformly oriented magnetic momenta. They were named after the French physicist Pierre-Ernest Weiss (1865–1940).
Weiss postulated in 1907[1][2] that the magnetic moment of atoms ("elementary magnets") of ferromagnetic materials become oriented within domains, even without an external magnetic field. The size of these oriented domains is in the range of 10-3 to 10-5 mm including a volume of about 106 to 109 atoms. The orientation is related to the crystal structure of the material.
By nature the Weiss domains are magnetized to the full saturation. The boundaries between the domains are called Bloch walls.
H. J. Williams used the powder pattern method in 1947-1949 to provided photos showing sizes and shapes of domains.[3] The powder pattern method uses a colloidal suspension of finely divided ferromagnetic material on the surface being studied, to make the boundaries visible with a microscope.[4]
Weiss domains are also found in ferroelectric materials (the electrical analogue of ferromagnetic materials), where the ferroelectric domains align to form regions of uniform dipole orientation.