page_title: Pyrolytic carbon
section_title: Magnetic levitation
hierarchical_section_title: Pyrolytic carbon / Magnetic levitation
caption_attribution_description: English: A small (~6mm) piece of pyrolytic graphite levitating over a permanent neodymium magnet array (5mm cubes on a piece of steel). Note that the poles of the magnets are aligned vertically and alternate (two with north facing up, and two with south facing up, diagonally)
context_page_description: Pyrolytic carbon is a material similar to graphite, but with some covalent bonding between its graphene sheets as a result of imperfections in its production.
  Pyrolytic carbon is man-made and is not thought to be found in nature. Generally it is produced by heating a hydrocarbon nearly to its decomposition temperature, and permitting the graphite to crystalize. One method is to heat synthetic fibers in a vacuum. Another method is to place seeds on a plate in the very hot gas to collect the graphite coating. It is used in high temperature applications such as missile nose cones, rocket motors, heat shields, laboratory furnaces, in graphite-reinforced plastic, coating nuclear fuel particles, and in biomedical prostheses.
context_section_description: Few materials can be made to magnetically levitate stably above the magnetic field from a permanent magnet. Although magnetic repulsion is obviously and easily achieved between any two magnets, the shape of the field causes the upper magnet to push off sideways, rather than remaining supported, rendering stable levitation impossible for magnetic objects (see Earnshaw's theorem). Strongly diamagnetic materials, however, can levitate above powerful magnets.
  With the easy availability of rare-earth permanent magnets in recent years, the strong diamagnetism of pyrolytic carbon makes it a convenient demonstration material for this effect.
  In 2012, a research group in Japan demonstrated that pyrolytic carbon can respond to laser light or sufficiently powerful natural sunlight by spinning or moving in the direction of the field gradient. The carbon's magnetic susceptibility weakens upon sufficient illumination, leading to an unbalanced magnetization of the material and movement when using a specific geometry.
caption: Pyrolytic carbon levitating over permanent magnets
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