Everything about Magnetization totally explained
Magnetization is a property of some materials (for example
magnets) that describes to what extent they're affected by
magnetic fields, and also determines the magnetic field that the material itself creates. Magnetization is defined as the amount of
magnetic moment per unit volume. The origin of the magnetic moments that create the magnetization can be either microscopic
electric currents corresponding to the motion of
electrons in
atoms, or the
spin of the electrons.
In some materials (for example,
ferromagnets) magnetization can exist even without an external magnetic field (
spontaneous magnetization). In other types of materials, magnetization is induced only when an external magnetic field is present. Magnetization isn't always
homogeneous within a body, but rather a function of position.
Magnetization in Maxwell's equations
The behavior of
magnetic fields (
.
Types of magnetism
Diamagnetism
This is the most common magnetic behavior. The
diamagnetic magnetization is proportional and opposing to the applied magnetic field. All materials present a diamagnetic response, although it may be shadowed by stronger magnetic behaviors. Diamagnetism can be explained by the normal response of the orbiting
electrons considering the
Lenz's law.
This is a weak form of magnetism that's non permanent and persists only while external field is applied. The magnitude of induced magnetic moment is very small and in a direction opposite to that of applied field. Therefore, relative permeability is less than 1 and
magnetic susceptibility is negative. When placed between the poles of a strong electromagnet, diamagnetic materials are pushed out towards the region where the field is weaker.
Paramagnetism
Paramagnetic materials present a magnetization that's proportional to the applied field and reinforces it. This arises from the existence of
magnetic dipoles in the material. Paramagnetism varies
inversely with
temperature and is characterized by the material's saturation magnetization.
Superparamagnetism
Superparamagnetic materials are paramagnetic materials whose magnetization saturates at very large fields. They are obtained using magnetic nanoparticle aggregates with large net magnetic moments. Each particle is a single magnetic domain. Consequently, the alignment of spins under applied field is no longer impeded by domain walls. Above the
blocking temperature, thermal vibrations randomly fluctuate the net spins, cancelling one another and the net moment of the collective particles is zero at zero field (no coercive field). If a magnetic field is applied, the particles will align producing a net moment. This behavior is characteristic of paramagnetic materials, but the difference is that each nanoparticle has a large net moment, so the saturation of magnetization occurs at very large fields of several teslas.
Ferromagnetism
Ferromagnetic materials present a magnetization much larger than other materials. Ferromagnetism arises from the strong coupling between the neighboring magnetic dipoles in the material. Ferromagnetic materials can present spontaneous magnetization, and this gives rise to the
hysteresis loops. Ferromagnetic materials can be characterized by their
permeability,
Curie temperature (temperature of the phase change to paramagnetic behavior),
coercive field (field strength needed to demagnetize the material), and remanent magnetization (magnetization at zero external field).
Nanomagnetism
On Feb-29-2008 it was announced that researchers from the
University of the Basque Country have achieved stable magnetization at a wide range of temperatures of
gold,
silver and
copper atoms.
Further Information
Get more info on 'Magnetization'.
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