Diamagnetic

Diamagnetism is a form of magnetism in which a material develops an induced magnetic field in opposition to an externally applied magnetic field, resulting in a very weak repulsion. It is a property of all materials and arises from the orbital motion of electrons, which create currents that oppose the change in magnetic flux. The effect is typically small and negative in sign.

Magnetic susceptibility for diamagnetic materials is negative and of very small magnitude, usually characterized by a volume susceptibility χv on the order of -10^-5 to -10^-6. Diamagnetic response is almost temperature independent, unlike paramagnetic materials, whose susceptibility increases with decreasing temperature following Curie’s law.

Mechanistically, when a magnetic field is applied, electrons rearrange their orbital motion to oppose the applied field, in line with Lenz’s law. The resulting induced magnetic moment cancels a part of the external field inside the material, yielding a net diamagnetic effect.

Common examples include bismuth, graphite, copper, quartz, water, and many organic compounds. While diamagnetism is usually weak, some materials exhibit noticeable diamagnetic responses and can be detected with sensitive instruments.

In nonuniform magnetic fields, diamagnetic materials experience a repulsive force from regions of higher field strength; in uniform fields, the effect is primarily a small change in energy with no net force. Diamagnetism is distinct from paramagnetism, which arises from unpaired electrons and attracts to magnetic fields, and ferromagnetism, which involves spontaneous magnetization.