A magnetic charge can behave and interact just like an electric charge in
some materials, according to new research led by the London
Centre for Nanotechnology (LCN) which could lead to a reassessment of current
magnetism theories, as well as significant technological advances.
The research, published today in Nature, proves the existence of atom-sized
magnetic charges called ‘magnetic monopoles’ that behave and interact
just like more familiar electric charges. It also demonstrates a perfect symmetry
between electricity and magnetism – a phenomenon dubbed ‘magnetricity'
by the authors from the LCN and STFC’s ISIS Neutron and Muon Source .
In order to prove experimentally the existence of magnetic current for the
first time, the team mapped Onsager's 1934 theory of the movement of ions in
water onto magnetic currents in a material called spin ice. They then tested
the theory by applying a magnetic field to a spin ice sample at a very low temperature
and observing the process using muon relaxation at ISIS, a technique which acts
as a super microscope allowing researchers to understand the world around us
at the atomic level.
The experiment allowed the team to detect magnetic charges in the spin ice
(Dy2Ti2O7), to measure their currents, and to determine the elementary unit
of the magnetic charge in the material. The monopoles they observed arise as
disturbances of the magnetic state of the spin ice, and can exist only inside
the material.
Professor Steve Bramwell, LCN co-author of the paper, said: “Magnetic
monopoles were first predicted to exist in 1931, but despite many searches,
they have never yet been observed as freely roaming elementary particles. These
monopoles do at least exist within the spin ice sample, but not outside.
"It is not often in the field of physics you get the chance to ask 'How
do you measure something?' and then go on to prove a theory unequivocally. This
is a very important step to establish that magnetic charge can flow like electric
charge. It is in the early stages, but who knows what the applications of magnetricity
could be in 100 years time."
Dr Sean Giblin, instrument scientist at ISIS and co-author of the paper, added:
“The results were astounding, using muons at ISIS we are finally able
to confirm that magnetic charge really is conducted through certain materials
at certain temperatures – just like the way ions conduct electricity in
water.”
Posted October 14th, 2009
