Paramagnétique

Paramagnétique describes a property of certain materials that are weakly attracted to an external magnetic field. When placed in a magnetic field, the atoms or molecules within a paramagnetic material possess unpaired electrons. These unpaired electrons have a magnetic moment, and in the absence of an external field, these moments are randomly oriented. However, when an external magnetic field is applied, these atomic magnetic moments tend to align themselves with the direction of the external field, resulting in a net magnetization in the same direction. This induced magnetization is proportional to the applied magnetic field strength, and the material is therefore attracted to the source of the field.

The susceptibility of paramagnetic materials is positive but small. Upon removal of the external magnetic field, the thermal agitation of the atoms causes the magnetic moments to return to their random orientation, and the material loses its induced magnetization. This is in contrast to ferromagnetic materials, which retain their magnetization even after the external field is removed. Examples of paramagnetic substances include aluminum, platinum, and oxygen. Paramagnetism is an important phenomenon in various scientific and technological applications, including magnetic resonance imaging (MRI) and the study of chemical compounds.