Physicists can come off like monster hunters sometimes–their theories predict that a rare beast lurks in the atomic-scale underbrush, so they forge on against all odds, determined to catch a glimpse of their quarry. The latest target is the magnetic monopole, and researchers say they’ve come closer than ever before to spotting it.
Every magnet has a north and a south pole; if you break a magnet into hundreds of pieces, each fragment will also have a north and a south pole of its own. But researchers think that magnetic monopoles exist–particles with only a north or south pole–and there are several reasons physicists would like to see them. In 1931, famed British theorist Paul Dirac argued that the existence of monopoles would explain the quantization of electric charge: the fact that every electron has exactly the same charge and exactly the opposite charge of every proton [ScienceNOW Daily News].
Scientists have scoured the world and the cosmos looking for such particles, says Jonathan Morris, coauthor of one of the two new studies published in Science. “People have been looking for monopoles in cosmic rays and particle accelerators — even Moon rocks” [Nature News], he says. And while the two research groups didn’t quite find the elusive particles, they did detect ripples in strange materials known as spin ices, and found that the ripples have the same magnetic properties as monopoles.
The two groups both used spin ices (one group used holmium titanate and the other used dysprosium titanate), which are man-made solid materials in which the magnetic ions line up like the hydrogen ions in water ice. The magnetic ions sit at the tips of four-sided pyramids or tetrahedra connected corner to corner…. At temperatures near absolute zero, they should organize themselves by a simple rule: In each tetrahedron, two ions point their north poles inward toward the center and two point outward [ScienceNOW Daily News]. But when researchers heated the materials slightly, the tidy magnetic properties of the spin ice was disrupted.
The heating caused tiny flaws in which one ion flipped, leaving its tetrahedron with three ions pointing their north poles inward; that meant the adjacent tetrahedron had only one ion pointing its north poles inward. These lopsided tetrahedrons act, respectively, like north and south magnetic poles. One imbalanced tetrahedron affects another, and the imbalance can flow through the material. These ripples create concentrations of either north or south poles, which amounts, essentially, to magnetic monopoles.
But to physicists like Kimball Milton, the experiments didn’t come close to achieving the ultimate goal of detecting a monopole particle. “I might object to [the researchers] saying ‘genuine magnetic monopoles’, because when you say genuine, that implies to me it’s a point particle, and it’s not,” Milton says. “It’s an effective excitation that at some level looks like a monopole, but it’s not really fundamentally a monopole” [Scientific American].
Looks like there are plenty more monopole hunting expeditions in our future.
Related Content:
DISCOVER: Three Words That Could Overthrow Physics: What Is Magnetism?
DISCOVER: More Magnets, Please
Image: T. Fennell, et al. / Science
September 10th, 2009 at 1:52 pm
They need to look north of the north pole or south of the south pole.
September 10th, 2009 at 4:59 pm
The problem is that magnetic monopoles are horny. Whenever you let one out it has to pair up immediately. That’s why I keep mine in a special air tight box.
September 10th, 2009 at 9:10 pm
How come so luky that the ’slightly heating’ cause a great initiate that will affect the whole cristal?
September 10th, 2009 at 9:43 pm
Cool.
September 11th, 2009 at 5:06 am
Q: How many monopoles does it take to turn on a light?
September 11th, 2009 at 11:55 am
Kimball Milton’s complaint was a propo . If these things are monopoles then we’ve had monopoles for a long time. If you take an ordinary solenoid and make it very long compared to the diameter then the magnetic field falls off like 1/r near each opening. We presume that if we ever find a magnetic monopole that there will be one of the opposite polarity somewhere else in the universe.
October 16th, 2009 at 9:30 am
When one is up to their arse in alligators, it’s too late to realize that their original intent was to drain the swamp.
Magnetic poles, which are ripples in the zero point energy field in space-time; are only produced by the action of electrons passing through this all encompassing field structure. The magnetic ripples are bi-polar due to the remaining quantum factors that prevent them from being frozen energy as an electron is described by e-mc^2. Magnetic poles are momentum existent, and are then a disturbance (ripple) in the ZPE field of the Fermion with motion. Ergo, the e=mc^2 relationship of matter and energy does directly apply to magnetic poles. They are not frozen energy like Fermions, but rather fluid in space-time. For the magnetic pole to become frozen energy, the Fermion itself would have to become fluid. Question for thought: Does a proton have a magnetic field?
October 16th, 2009 at 12:16 pm
drdeak’s drivel suggests that indeed the real question is not: Do magnetic monopoles exist? But the question is: Do electric monopoles exist? It has been suggested that the flux from an electric monopole goes through what amounts to a wormhole and terminates on a charge of the opposite polarity. Indeed, since the vacuum EM field is polarized near a charge so there are so many charges arbitrarily close to what we call the monopole that we can never completely do an experiment to pick out the field right at the “origin”. The best we can do is find that the requirement of unitarity (a particular way of being single valued) requires a term which says that leptons scatter like points rather than like particles with internal structure (even fuzzy structure).
October 16th, 2009 at 12:31 pm
What I still don’t get about this experiment is: the definition of a monopole is: If you add up all the flux going through a surface surrounding the monopole you get a non-zero result. If you surround the tetrahedron, you must get zero since there a 4 N and 4 S. So modelling our thinking after my comment in #6, that means that all the flux pointed inward has to squish out a tiny tube to terminate on another tetrahedron. Where is that squish point? Aha. Suppose the inward pointing poles are S; put them on the base. So there are 3 S on the base pointing up and 1 S at the peak pointing up. 3 N on the base pointing down and 1 N on the peak pointing down. So we have a net of 3 S pointing up but squished toward the peak and 3 N pointing down and rather mother diffuse. IOW we don’t have a magnetic dipole field, but we do have a magnetic quadrapole field plus a magnetic monopole field. The addition of the quadrapole term is really crucial.
October 16th, 2009 at 8:49 pm
I should have mentioned HOW drdeak’s post is drivel. It partly comes from the notion of the ZPF. Although on average a ZPF would have the requisite Higgs particle scalar nature (and being an infinite average that’s pretty helpful), it’s still created from vector particles of photons. As a Higgs wannabe, it inherits the Higgs’ problem of not having an intrinsic coupling constant so one is just substituting one unknown (the Fermion electron/lepton/quark mass) for another (the coupling constant for the particular Fermion). However, at least for the Higgs model, right handed and left handed Fermions would have one coupling constant from the way they are projected out of the Dirac equation; for the ZPF model, there is no reason for the coupling constant for the right handed to be the same as for the left handed particles. Thus the notion of making the invisible ZPF field infinite (to maintain isosymmetry) still would have different physics in different directions of space and at random. Plus the fluid notion says nothing. The proton question says nothing; does he mean do the individual quarks have magnetic fields or does the proton have a field (which it does and which has been measured).