What materials do magnets repel?
Magnets possess the quality to attract some metals yet repel others. The materials that magnets repel are diamagnetic. They contain only paired electrons spinning in opposite directions around the nucleus, thereby cancelling each other out and producing no magnetic field.
The repelling force of these materials is far weaker than magnetic attraction of ferromagnetic materials. Other than water, materials with the strongest diamagnetic force are carbon graphite, bismuth and silver.
Diamagnetic materials repel magnets at the point of their greatest magnetic field. Because the diamagnetic effect is dim, it takes two substantial pieces of diamagnetic materials surrounding a small, powerful magnet to repel the magnet, or push it in opposite directions and making it appear to levitate.
Narrowly sliced carbon graphite has a negative magnetic susceptibility. This material provokes weak diamagnetic fields in the presence of magnetic fields. Carbon graphite floats in a magnetic field of rare earth permanent magnets. Carbon graphite is not the same as plain graphite, used in pencils, which has the opposite quality of ferromagnetism.
The most readily available form of bismuth is found in shotgun pellets. It needs to be melted down and poured into something like a cupcake pan to form diamagnetic plates. It expands while cooling, where it can more easily demonstrate the diamagnetic effect. Bismuth is the most strongly diamagnetic material. It boasts a high electrical resistance while in a magnetic field. Like carbon graphite, it possesses about 20 times greater diamagnetism than water.
Silver is near copper on the Periodic Table, and is the strongest electrical and thermal conductor. It has a low resistance which allows electricity to pass easily through it. It is more strongly diamagnetic than copper, repelling any magnetic flow that tries to penetrate it. It will produce a current when exposed to a strong enough magnet. It will produce an opposing magnetic field when electrical current runs through it.