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April 12, 2010

New material mimics a magnetic monopole at Room Temperature

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Researchers from Imperial College London have created a structure that acts like a single pole of a magnet, a feat that has evaded scientists for decades. The researchers say their new Nature Physics study takes them a step closer to isolating a ’magnetic monopole.
Magnets have two magnetic poles, north and south. ‘Like’ poles, such as north and north, repel one another and ‘opposite’ poles, such as north and south, attract. Whichever way a magnet is cut, it will always have these two poles. Scientists have theorised for many years that it must be possible to isolate a ‘magnetic monopole’, either north or south on its own, but until recently researchers have been unable to show this in experiments. Researchers at Imperial have now enabled tiny nano-sized magnets to behave like magnetic monopoles, by arranging them in a honeycomb structure. In late 2009, various teams of scientists reported they had created monopole-like behaviour in a material called ‘spin ice’. In these materials, monopoles form only at extremely low temperatures of -270 degrees Celsius. The Imperial researchers’ structure contains magnetic monopoles at room temperature.
Nature Physics - Direct observation of magnetic monopole defects in an artificial spin-ice system
Free monopoles have fascinated and eluded researchers since their prediction by Dirac in 1931. In spin ice, the bulk frustrated magnet, local ordering principles known as ice rules—two-in/two-out for four spins arranged in a tetrahedron—minimize magnetic charge. Remarkably, recent work shows that mobile excitations, termed ‘monopole defects’, emerge when the ice rules break down. Using a cobalt honeycomb nanostructure we study the two-dimensional planar analogue called kagome or artificial spin ice. Here we show direct images of kagome monopole defects and the flow of magnetic charge using magnetic force microscopy. We find the local magnetic charge distribution at each vertex of the honeycomb pins the magnetic charge carriers, and opposite charges hop in opposite directions in an applied field. The parameters that enter the problem of creating and imaging monopole defects can be mapped onto a simple model that requires only the ice-rule violation energy and distribution of switching fields of the individual bars of a cobalt honeycomb lattice. As we demonstrate, it is the exquisite interplay between these energy scales in the cobalt nanostructure that leads to our experimental observations.
92 pages of supplemental information

Hans Moravec on Applications of True Magnetic Monopole Atom or Particle
The current Imperial College does not have magnetic monopole particles.
The predictions of some gauge theories that monopoles exist and the smallest weigh about 1000 protons.
* Monopole atoms are 2 million times as close as conventional atoms.
* Combined with increased attraction due to the magnetic quantum being (68.5)^2 as strong as electric, the tensile strength of monopolium is (2,000,000)^4x(68.5)^2 = 10^29 as high as normal. * The strength to weight ratio is thus about 10 million times as high.
Magnetic monopole at wikipedia
Magnetic monopole particles would be similar to stable matter from subatomic particles (femtotech)
Particle Accelerators continue to Search for Monopole Particles



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