![]() The resulting induced magnetic field opposes the original field, resulting in a total field that is less than originally imposed. The result is the production of induced magnetic dipoles that anti-align with the field, as happens with the electrons in a plasma. However, the magnetic field still distorts the motions of electrons via the Lorentz force. If there are no unpaired electrons in a material, then there are no pre-existing dipoles to align. The temperature at which this occurs for a particular material is called the Curie temperature. Since it is a vector quantity, it also has a. It can be mathematically expressed as, m 2a ×qm 2qma m 2 a × q m 2 q m a. If this jiggling becomes strong enough, the tendency of neighboring dipoles to maintain a common orientation is overcome and the material becomes paramagnetic. Magnetic dipole moment of a magnetic dipole is basically a vector quantity whose magnitude,m, is a product of the pole strength, ( qm q m) and the distance 2a between the poles. As the temperature increases, the thermal jiggling of atoms increases in proportion. “Permanent” magnets may be created this way. ![]() In this case the imposition of an external magnetic field causes very strong dipole alignment effects to the point where interactions between the newly aligned dipoles prevent the reversion to random orientation when the imposed field is removed. If the imposed magnetic field is taken away, the atoms reorient themselves randomly, resulting in zero field.Ī few materials, such as iron, exhibit a more complex phenomenon called ferromagnetism. The midpoint q and q is called the centre of the dipole. By default, the direction of electric dipoles in space is always from negative charge -q to positive charge q. If a magnetic field is imposed, this dipole tends to align with the magnetic field, which in turn reinforces the imposed field, resulting in a stronger total field. An electric dipole is defined as a couple of opposite charges q and q separated by a distance d. In this case, there is a net magnetic dipole moment for each atom. Paramagnetism occurs when atoms have an odd number of electrons, which means that the angular momentum of these electrons does not add up to zero (see next chapter). Magnetic dipoles from orbital and spin angular momenta have important practical consequences they are central to the phenomena of paramagnetism and ferromagnetism. ) results from relativistic factors, but the derivation is rather complex, so we will not present it here.
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