Paramagnetism refers to the tendency of the atomic magnetic dipoles, due to quantum-mechanical spin , in a material that is otherwise non-magnetic to align with an external magnetic field. This alignment of the atomic dipoles with the magnetic field tends to strengthen it, and is described by a relative magnetic permeability greater than unity (or, equivalently, a small positive magnetic susceptibility).

In pure paramagnetism, the field acts on each atomic dipole independently and there are no interactions between individual atomic dipoles. Such paramagnetic behaviour can also be observed in ferromagnetic materials that are above their Curie temperature.

Paramagnetic materials attract and repel like normal magnets when subject to a magnetic field. Under relatively low magnetic field saturation when the most of the atomic dipoles are not aligned with the field, paramagnetic materials exhibit magnetisation according to Curie's Law:

In the above equation, M is the resulting magnetisation, B is the magnetic flux density of the applied field, T is absolute temperature (Kelvin), and C is a material-specific Curie constant. This law indicates that paramagentic materials tend to become increasingly magnetic as the applied magnetic field is increased, but less magnetic as temperature is increased.

See also: diamagnetism, ferromagnetism, Pierre Curie.