Weiss domains
Encyclopedia
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 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 wall
s.
H. J. Williams used the powder pattern method in 1947-1949 to
provided photos showing sizes and shapes of domains.
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.
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.
Crystal structure
In mineralogy and crystallography, crystal structure is a unique arrangement of atoms or molecules in a crystalline liquid or solid. A crystal structure is composed of a pattern, a set of atoms arranged in a particular way, and a lattice exhibiting long-range order and symmetry...
of a ferromagnetic
Ferromagnetism
Ferromagnetism is the basic mechanism by which certain materials form permanent magnets, or are attracted to magnets. In physics, several different types of magnetism are distinguished...
material with uniformly oriented magnetic momenta. They were named after the French physicist
Physicist
A physicist is a scientist who studies or practices physics. Physicists study a wide range of physical phenomena in many branches of physics spanning all length scales: from sub-atomic particles of which all ordinary matter is made to the behavior of the material Universe as a whole...
Pierre-Ernest Weiss (1865–1940).
Weiss postulated in 1907 that the magnetic moment
Magnetic moment
The magnetic moment of a magnet is a quantity that determines the force that the magnet can exert on electric currents and the torque that a magnetic field will exert on it...
of atoms ("elementary magnets") of ferromagnetic materials become oriented within domains,
even without an external magnetic field
Magnetic field
A magnetic field is a mathematical description of the magnetic influence of electric currents and magnetic materials. The magnetic field at any given point is specified by both a direction and a magnitude ; as such it is a vector field.Technically, a magnetic field is a pseudo vector;...
. 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
Saturation (magnetic)
Seen in some magnetic materials, saturation is the state reached when an increase in applied external magnetizing field H cannot increase the magnetization of the material further, so the total magnetic field B levels off...
. The boundaries between the domains are called Bloch wall
Bloch wall
A Bloch wall is a narrow transition region at the boundary between magnetic domains, over which the magnetization changes from its value in one domain to that in the next. The magnetization rotates along an axis that is perpendicular to the plane of the wall unlike the Néel wall where the...
s.
H. J. Williams used the powder pattern method in 1947-1949 to
provided photos showing sizes and shapes of domains.
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.
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.