paramagnetie

Paramagnetism is a form of magnetism that occurs only in the presence of an external magnetic field. Materials exhibiting paramagnetism are weakly attracted to the external field and become magnetized in the same direction as the applied field. This attraction is generally much weaker than that observed in ferromagnetic materials.

The origin of paramagnetism lies in the behavior of unpaired electrons within the atoms of the material. Each unpaired electron possesses a magnetic dipole moment. In the absence of an external magnetic field, these individual magnetic moments are randomly oriented, resulting in no net magnetization. However, when an external magnetic field is applied, these atomic magnetic dipoles tend to align themselves with the field, creating a net magnetic moment.

The strength of this alignment is temperature-dependent. As temperature increases, the thermal motion of the atoms becomes more vigorous, tending to disrupt the alignment of the magnetic dipoles. Consequently, the magnetic susceptibility of a paramagnetic material decreases with increasing temperature, a relationship often described by the Curie law.

Common examples of paramagnetic materials include aluminum, platinum, oxygen, and most alkali and alkaline earth metals. These materials are not inherently magnetic and lose their magnetism once the external field is removed. The effect is subtle and requires sensitive measurement techniques to detect.