A magnet attracts iron when, by applying a magnetic field, its elementary magnets align.
If we now do the same procedure with a diamagnetic material, that is, materials that are weakly magnetized, such as copper, we will see that the reverse process of what happened with the piece of iron will occur. When applying a magnetic field on this material, its elementary magnets will align in the opposite direction to the direction of the field being applied, then the repulsion between this material and the magnet will occur. This fact was first observed by Faraday, in the 19th century, when he brought a sample of bismuth, also a diamagnetic substance, close to a magnet and saw that it was repelled, contrary to what happened with the pieces of iron he was already exposed to. used to see.