I just acquired some pyrolitic graphite and powerful neodymium magnets from United Nuclear. Pyrolytic graphite has the highest diamagnetism of any room temperature material [see correction below]:
Diamagnetism is the property of an object which causes it to create a magnetic field in opposition to an externally applied magnetic field, thus causing a repulsive effect. Specifically, an external magnetic field alters the orbital velocity of electrons around their nuclei, thus changing the magnetic dipole moment. According to Lenz's law, these electrons will oppose the magnetic field changes provided by the applied field, preventing them from building up. The result is that lines of magnetic flux curve away from the material.Here are some small pieces of pyrolitic graphite on top of four 0.5" square neodymium magnets:
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This is not magnetic repulsion. If that were the case the pieces of graphite would simply fly off the magnets. The magnetic field is strongest at the edges of the magnets so the largest piece is trapped in the center; it's pushed inward to the point of least magnetism. If perturbed it will snap back to this same point and orientation. The smaller pieces are standing on edge because they are repelling the magnetic field on both sides and can't fall over. If one is pushed over it will immediately snap back into a vertical position.
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Superconductors have an even more powerful diamagnetic effect but require liquid nitrogen to cool them sufficiently.
I'll have more on this topic in the future as I've also acquired some bismuth, which has the highest room temperature diamagnetism of any metal.
Here's the difference between bismuth and pyrolitic graphite (without the math):
"The most strongly diamagnetic material is bismuth, although pyrolytic carbon may have a [lower] susceptibility in one plane."
So there you have it. I played around with some bismuth the other day and it was quite interesting. Stay "tuned"...