Carbon's mysterious magnetism.An X-ray experiment has produced the most conclusive evidence CONCLUSIVE EVIDENCE. That which cannot be contradicted by any other evidence,; for example, a record, unless impeached for fraud, is conclusive evidence between the parties. 3 Bouv. Inst. n. 3061-62. yet that carbon can be made into a permanent magnet.
Only a few elements are magnetic at room temperature. They are metals whose atoms have a magnetic moment arising from the spin of an unpaired electron. Pairs of electrons with opposite spin produce no net magnetic moment. Since carbon tends to form covalent bonds, which contain paired electrons, it seems an unlikely candidate to be magnetized.
But several experiments have suggested that under certain conditions, forms of bulk carbon such as graphite can acquire a feeble permanent magnetization. Most physicists regard these results with skepticism, however, since even trace contamination by a metal such as iron could make a sample slightly magnetic.
Now, a team led by Hendrik Ohldag of the Stanford (Calif.) Synchrotron synchrotron: see particle accelerator.
Cyclic particle accelerator in which the particle is confined to its orbit by a magnetic field. The strength of the magnetic field increases as the particle's momentum increases. Radiation Laboratory has found magnetism in a sample of graphite that had been irradiated with protons. The researchers detected a magnetic moment through the effect it had on the absorption of polarized A one-way direction of a signal or the molecules within a material pointing in one direction. X rays. To rule out contamination, they tuned the energy of the X rays so that they interacted with carbon atoms but not with iron atoms. The results appear in the May 4 Physical Review Letters Physical Review Letters is one of the most prestigious journals in physics. Since 1958, it has been published by the American Physical Society as an outgrowth of The Physical Review. .
Ohldag says that the proton bombardment could have permanently deformed the hexagonal lattice The hexagonal lattice or equilateral triangular lattice is one of the five 2D lattice types.
Three nearby points form an equilateral triangle. In images four orientations of such a triangle are by far the most common. of carbon atoms in graphite, creating some non-covalent bonds between atoms.