Oct
19
About the New Magnetic Electricity
October 19, 2009 | 4 Comments
Researchers in the U.K. have discovered a magnetic equivalent to electricity – single magnetic charges that can behave and interact like electrical ones. The implications are significant if not fully understood or thought out to the possibilities. The potential will change as more experimenters achieve seeing the phenomena, thus offering more ideas on where the magnetic electricity could lead.
Back in 1931 physicist Paul Dirac hypothesized that on the quantum level, magnetic charges must exist in discrete packets, or as quanta, in the same way that electric energy exists in photons. That implied the existence of magnetic monopoles – particles that have a single magnetic charge, or polar identity, of either north or south. For the past 78 years Dirac’s speculation interested only hardcore theorists, because the conjecture failed to find any expression in observed phenomena. All magnets had two poles, one north and one south, inextricably attached to each other.
Cut a magnet in two and you get two magnets each with north and south poles. Except all that changed in September, when teo teams of physicists discovered the identity carrying particle Dirac predicted, as well as the one-poled magnets the particle creates. These magnets, called monopoles, exist only (so far) in special crystals called “spin ice,” which can’t form regular magnets due to the forces generated by the unique geometry in their crystal bonding structure.
These crystals are made up of pyramids of charged atoms, or ions, arranged in such a way that when cooled to exceptionally low temperatures, the materials show tiny, discrete packets of magnetic charge.
The U.K. research group is led by Steven Bramwell of the London Centre for Nanotechnology. The team has managed to measure the amount of magnetic “charge” on the monopoles and to measure magnetic analogues to electric current for the first time. The team calls the motion and interaction of monopoles “magnetricity”. The paper about the experiment is now available online in Nature.
To get more detailed information on the monopoles than had previously been possible, Bramwell’s team injected muons – short-lived cousins of electrons created at the Science and Technology Facilities Council’s ISIS neutron and muon source near Oxford – into the spin ice. When the muons decayed, they emitted positrons in directions influenced by the magnetic field inside the spin ice. This revealed that the monopoles were not only present but were moving, producing a magnetic current.
They showed that when the spin ice was placed in a magnetic field, the monopoles piled up on one side – just like electrons would pile up when placed in an electric field.
It also allowed the team to measure the amount of magnetic charge on the monopoles. It turned out to be about a 5 in the obscure units of Bohr magnetons per angstrom, in close agreement with theory, which predicted 4.6. Unlike the electric charge on electrons, which is fixed, the magnetic charge on monopoles varies with the temperature and pressure of the spin ice.
Magnetricity - Magnetic Wien Effect. Click image for more information.
In an accompanying commentary in Nature Shivaji Sondhi of Princeton University in New Jersey, a spin ice researcher who is not a member of Bramwell’s team called the new achievement “a triumph of a bold experimental foray. The experiment itself and the determination of the charge of magnetic monopoles are striking.”
Bramwell says, “It is in the early stages, but who knows what the applications of magnetricity could be in 100 years time.”
Right at the start the suggested use could be the possibility that magnetic monopoles might be used for computer memory and storage. If magnetic polar identity can flow through crystals of spin ice, then the current of identity could replace positive and negative charges with positive and negative monopoles as the information storage medium. Since controlling the magnetic identity of electrons underlies quantum computing, this ability to alter that identity with a current might position spin ice as the new leading candidate for quantum computing chips.
The sage observers will realize that as magnetism and electricity were curiosities in the early days, magnetricity will also be subjected to the imaginations of the contemporaneous Tesla and others. We haven’t seen but just the start of where magnetricity could go. At the rate information moves about, the desires of creative people to discover attributes and uses, and the world’s effort to get more work accomplished at lower energy inputs suggests that the ideas of today about magnetricity are only seeds of future ideas.
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