Nonmagnetic

Nonmagnetic is a term used to describe materials that exhibit little to no permanent magnetic moment and show only a negligible response to external magnetic fields under ordinary conditions. In physics, this is often expressed by a very small magnetic susceptibility, indicating that the material does not become strongly magnetized when exposed to a magnetic field. In practice, many materials labeled nonmagnetic are either diamagnetic or weakly paramagnetic; their magnetic responses are typically small compared with ferromagnetic materials and may be easily overwhelmed by stronger effects in real measurements.

Diamagnetism and paramagnetism are the two main ways a nonferromagnetic material can respond to a field. Diamagnetic materials develop an induced magnetic moment opposite to the applied field, resulting in a weak repulsion. Paramagnetic materials align their unpaired electrons with the field, producing a weak attraction. Both responses are usually small and reversible when the field is removed.

Common nonmagnetic materials include many metals such as copper, aluminum, silver, and gold, as well as glass, wood, and most plastics. These materials are often chosen for applications where magnetic interference must be minimized, such as in precision instrumentation, electronics, or medical devices. They are also preferred for implants in magnetic resonance imaging (MRI) environments to avoid image distortion.

Measurement and context matter: magnetic behavior is described quantitatively by magnetic susceptibility and permeability, and the classification of a material as nonmagnetic depends on the field strength, temperature, and the comparison to materials with strong magnetic ordering.