Exchange spring magnet
The magnetostatic energy is the energy stored in the field generated by a material's magnetic moments. The magnet's field reaches its maximum intensity if all the magnetic moments orient in one direction; this is what occurs in a hard magnet. In order to prevent building up the magnetic field, sometimes magnetic moments tend to form loops. That way, the energy stored in the magnetic field can be constrained; this is what occurs in a soft magnet. What determines whether a magnet is hard or soft is the dominant term of its magnetic energy. For hard magnets, the anisotropy constant is relatively large, making the magnetic moments align with easy axis. The opposite case applies to soft magnets, in which the magnetostatic energy is dominant.
Magnetic field
The term 'magnetic field' is used for two distinct but closely related fields denoted by the symbols and . In the International System of Units, is measured in units of amperes per meter and is measured in teslas, which are equivalent to newtons per meter per ampere. and differ in how they account for magnetization. In a vacuum, and are the same aside from units; but in a magnetized material, /formula_1 and differ by the magnetization of the material at that point in the material.