Materials that Faraday classified as repelled by a magnetic field are called diamagnetic.
Diamagnetic materials develop an induced magnetic response opposite to the applied field, producing a weak repulsion. Faraday investigated this behavior in 1845 and concluded that matter generally responds magnetically, even when the effect is too small to notice in everyday life.
The term was suggested by William Whewell, using the Greek prefix dia-, meaning “through” or “across.” Faraday contrasted diamagnetic substances with paramagnetic ones, which are weakly attracted to a magnetic field. Ferromagnetic materials, such as iron, show a much stronger attraction because of aligned magnetic domains.
Diamagnetism is a subtle quantum effect present in all materials, although it may be overwhelmed by stronger forms of magnetism. In ordinary diamagnetic substances, electrons are paired; notable examples include bismuth, copper, water, and graphite. Superconductors provide an extreme example because they expel magnetic fields through the Meissner effect.