The magnetization field or M-field can be defined according to the following equation:
Where is the elementary magnetic moment and is the volume element; in other words, the M-field is the distribution of magnetic moments in the region or manifold concerned. This is better illustrated through the following relation:
where m is an ordinary magnetic moment and the triple integral denotes integration over a volume. This makes the M-field completely analogous to the electric polarisation field, or P-field, used to determine the electric dipole moment p generated by a similar region or manifold with such a polarization:
Where is the elementary electric dipole moment.
Those definitions of P and M as a "moments per unit volume" are widely adopted,
though in some cases they can lead to ambiguities and paradoxes.
The M-field is measured in amperes per meter (A/m) in SI units.
The magnetization is often not listed as a material parameter for commercially available ferromagnets. Instead the parameter that is listed is residual flux density, denoted . Physicists often need the magnetization to calculate the moment of a ferromagnet.
To calculate the dipole moment m (A⋅m2) using the formula:
we have that
- is the residual flux density, expressed in teslas (T).
- is the volume (m3) of the magnet.
- H/m is the permeability of vacuum.