POLE POSITION: Can magnetic north exist independent of magnetic south?
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Magnets are remarkable exemplars of fairness—each north pole is invariably accompanied by a counterbalancing south pole. Split a magnet in two, and the result is a pair of perfectly neutral magnets, each with its own north and south.
For decades researchers have sought the exception to this rule of fairness and balance: the magnetic monopole. Magnetism's answer to electricity's negatively charged electron, a monopole would be a free-floating carrier of either magnetic north or magnetic south—a yin unbound from its yang.
A pair of papers published online this week in Science offer experimental evidence that such monopoles do in fact exist, albeit not as electron-like elementary particles, a caveat that one self-professed purist says disqualifies them from genuine monopole status.
Both studies examine the magnetic behavior of a family of rare-earth materials known as spin ices—one group using holmium titanate and the other dysprosium titanate. The man-made spin ices take their name from their similarity to water ice—at the molecular level their internal magnetic structure is analogous to the arrangement of protons in ice.
Claudio Castelnovo, a postdoctoral physicist at the University of Oxford who co-authored one of the Science papers and also co-wrote a paper in Nature last year describing how monopoles might be realized in spin ices, explains that the compounds offer a peculiar combination of order and freedom that facilitates the dissociation of the poles.
At low temperatures, there is still some magnetic wiggle room in the spin ice's lattice structure, but not a lot—the magnetic freedom of the system is frustrated, so to speak. "As a result, this is a substance that has degrees of freedom that look the same, microscopically, as you would see in a fridge magnet," Castelnovo says. "But a fridge magnet is able to order so as to act as a fridge magnet and stick to metals, while this one is not able to achieve this level of ordering in spite of having this magnetic structure inside, because of this frustration."
Internally, the tiny magnetic components arrange themselves head to tail in strings, like chains of bar magnets stretching across a table in different directions. In a very cold, clean sample, those strings form closed loops. But excitation induced by a rise in temperature can introduce tiny defects in these chains, Castelnovo says—in the bar-magnet analogue, one of the magnets is flipped, breaking the head-to-tail continuity. "You have your path that is north–south–north–south, and at a certain point one of the needles actually twists 180 degrees and points the wrong way," he explains.
On either side of that defect, all of a sudden, is a concentration of magnetic charge—two norths at one end, two souths at the other. Those concentrations can float free along the string, acting as—voilà—magnetic monopoles.
"The beauty of spin ice is that the remaining degree of disorder in this low-temperature phase makes these two points independent of each other, apart from the fact that they attract each other from a magnetic point of view because one is a north and one is a south," Castelnovo says. "But they are otherwise free to move around."
Of course, this method of synthesizing monopoles cannot bring a north into existence without also generating a south—the key is their dissociation. "They always have to come in pairs," Castelnovo says, "but they don't have to be anywhere specifically in relation to one another."
But Kimball Milton, a University of Oklahoma physicist who wrote a 2006 review article summarizing the status of monopole searches, is not convinced. "These are not magnetic monopoles," he says.
"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."
He also says it is "completely wrong" to describe, as the research teams do, the chain of magnetism within spin ices as a Dirac string, a hypothetical invisible tether with a monopole at its end that was envisioned in the 1930s by English physicist Paul Dirac. "But that's just because I'm a purist," Milton says.
By his assessment, the magnetic strings in the spin ice do not fit the Dirac definition because they are, in fact, observable and merely carry flux between two opposing so-called monopoles. "Real monopoles, if they existed, would be isolated, and the string would run off to infinity," he says.
"I'm not trying to put down the experiment or the work in any way," Milton says. "I'm sure [the new studies] are important in the field of condensed matter physics. They're not important from a fundamental point of view."
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23 Comments
Add CommentIs it just me, or is this an analogue to a transistor?
Reply | Report Abuse | Link to thisInfinity does not exist.
Reply | Report Abuse | Link to thisJust because your brain can not comprehend infinity does not mean it does not exist.
Reply | Report Abuse | Link to thisIf a monopole can exist and if it can be made much larger wouldn't that be able to be used to counter act the Earths magnetic field - so objects would "fall up" ?
Reply | Report Abuse | Link to thisMagnetism is not gravity
Reply | Report Abuse | Link to thisMagnetic monopoles may exist but the methods we are using to find them is counterintuitive meaning every time we try to find them they disappear similar to the effect of light and atoms passing through the slits, every time we go to measure them the effect disappears.
Reply | Report Abuse | Link to thisAll we may need is an ingenious type of measuring tool to fool magnetic monopoles in thinking we aren't looking for them...
Sounds like a topological spin defect, a quasiparticle, an excitation above the ground state. A soliton, maybe. Solids have lots of such things, many of which behave strangely. E.g., some experiments indicate that charge carriers in Aluminum have positive charge. Another quasiparticle, the "Bloch electron", can slow down when you add energy. This thing is not monopole in the sense of the elementary particles, which is the only sense that would be truly remarkable. OTOH, it will often behave just like a true monopole.
Reply | Report Abuse | Link to thisI was originally designing a machine to travel via the magnetic lines of force in the earth' s atmosphere, but due to a shortage of magnetic monopoles, the project is temporarily in hiatus. My current vehicle design will travel by hooking on to the lines of longitude and pulling itself forward.
Reply | Report Abuse | Link to thisRead the article again, their monopoles are just very small crystal horseshoe magnets. Magnetic lines of force are circulating closed circuits of energy that flow in the direction of magnetic S pole to N pole. Monopoles can not exist as energy must be conserved, circulated in and out. Protons create magnetic force fields around them selves, generally they oppose and cancel but some align and create fields that effect the larger world. Think of a rubber band that is spinning along it's length the stronger the energy the larger it gets, the greater the amount of energy the more lines of force.
Reply | Report Abuse | Link to thisIn the knowledge range of mine, the so -called monopoles only exist in theory level recently. As it is said in the article, researchers have found "monopoles" at low-temperature atmospher. It maybe that in such freeze situation, the movement of molecules have been limited so that they can not form N pole and S pole, thus belie the genuine two poles phenomenon. It is only a temporary phenomenon! And I also wonder that if monopoles do exist, how it could affect the creaters on the earth!
Reply | Report Abuse | Link to thisAnaglolusly, a positive "hole" in a semiconductor, while behaving like a positive electron, in certainly not a positron.
Reply | Report Abuse | Link to thisIt looks like a virtual monopole to me. Just as a positive "hole" in a semiconductor act like a positive electron, it is not a positron.
Reply | Report Abuse | Link to thisThis is amazing, the existence of monopoles at very low temperature. Quite a bit of daring scientific speculation, qualified as usual with words like “can’, “likely”, “appears” etc.
Reply | Report Abuse | Link to thisLet there be more concrete evidence first before making any further such sensational announcement. In fact, the comments made by a few responsible readers have been relevant.
A recent experiment proved Einstein was right, gravity warps space and slows time.
Reply | Report Abuse | Link to thisWe live in a baryonic universe, eventually all these particles are going to fall into black holes, it follows from logic that if gravity slows time it must stop time in a black hole.
When the entire baryonic content of the universe ends up in one or more black holes time cease to be. No time no infinity.
Infinity is the hypothetical creation of religion, grabbed on to wholeheartedly by mumbo-jumbo scientists called economists. Fundamental to their so called science is the existence of infinite resources, infinite markets and infinite money. Now you know why economic theory never gets things right, busts and booms are the economists tool to loot the masses.
Wow. Magnetic monopoles!
Reply | Report Abuse | Link to thisSo are these things true monopoles, or just small assemblages that act or appear to be monopoles, with the corresponding "other" pole just hidden or inaccessible to us on a human scale?
For a layman's analogy, Here is how I would describe a macro model of a monopole, if I understand correctly (please critique).
I take a solid sphere "SS" of magnetic material (as yet unmagnetized), cut it up into "b" identical spherical sections, magnetize each section identically with say, the N pole at the apex and the S pole at the original sphere's surface. In other words, the magnetization is oriented radially relative to the original sphere. I then reassemble all the segments back into a sphere (with some effort, since I must force all the N poles together) and fasten them together, perhaps with glue. I now have a sphere with "b" S poles on its surface, and no discernable N poles. If I make "b" a very large number, the S poles will all appear to merge, with still no N poles in sight.
Would the reassembled "SS" be a decent macro model for the micro phenomenon described? I have to guess not, or monopoles would not be so elusive to science. In that case, can anyone explain the difference between my model and the real thing? Where is it wrong?
If the answer is that the tip of the apexes (apices?) have too dense a magnetic field, then how about using a hollow sphere "HS" similar in geometry to the rubber ball inside a tennis ball? Cut it into "b" identical sectors, magnetize each in a radial pattern with N to the inside of the sphere (the concave face of the sector) and reassemble as before...
To extend this thought experiment a bit, what would an observer detect if s/he were trapped inside "HS"? How would their magnetic compass behave? And if instead of a person and their compass there were an originally-unmagnetized small sphere of magnetize-able material that could become magnetized (I don't know how - through temperature cycling?) while inside "HS", would it too become a magnetic monopole (albeit perhaps of opposite polarity - i.e. S hidden and N displayed on its surface)?
Ice spin magnets monopoles, are Natural compositions, not necessary a genuine natural magnet,
Reply | Report Abuse | Link to thisLet us get-off of such non-productive subjects.
The possibility of Monopoles is in the electro-magnetism subjects, it is very possible, and it is just common sense.
So I can build a parachute that modifies my body's response to the force of gravity, that doesn't mean I've changed the laws of physics. Heck, if I take two bar magnets and find a way to glue the two south poles together to overcome their natural repulsion, I can claim to have made a bar magnet with two north poles, if I ignore what is going on in the middle.
Reply | Report Abuse | Link to thisWhat I mean is; just because in some exotic and ephemeral way someone has created a situation that temporarily restructures the lines of force of a substance under conditions that prevent them from responding naturally to the energy of these lines of force doesn't mean they have created a monopole. They have merely found a way to block the materials from responding to the flow of energy inherent in their structure.
Now, that doesn't mean the experiment might not have introduced a useful technique for some purpose later on. I hear parachutes are very useful to have around in an emergency.
That was a silly statement. Infinity does exist. Start counting. Let me know when you get to the end.
Reply | Report Abuse | Link to thisOr, Yes, it does. Because we are unable to step outside this universe, there can indeed be a pattern without end. Infinity.
Or, Yes it does. I just thought of it.
Or, Yes it does. Does it matter what I write anymore so long as I write Or,?
See? No? I'm sorry. Try again later.
"A recent experiment proved Einstein was right, gravity warps space and slows time."
Reply | Report Abuse | Link to thisWhat recent experiment? Your full of shite.
"We live in a baryonic universe, eventually all these particles are going to fall into black holes, it follows from logic that if gravity slows time it must stop time in a black hole."
A baryonic Universe?? Who told you that? How funny. Have YOU thought about it. I think not. Just because protons and neutrons are considered baryons? Cooool!!!
I, Sleekmason, Claim all matter is composed, of . . Funk! Therefore, logic assumes we live in a Funky Universe. Moron.
I get really teed off at people like you who detract from valid questions about our existence. I don't want to wade through your garbage to find the implications you cant percieve.
Yes, religion is bunk, but karma/spirituality/thought, for lack of a better term, still has force for us chimps.
Quit posting smack to sound good. Get a life. What are you, 22? Just tell the chicks your George Clooneys cousin.
I will say though, that you are indeed correct to question all you see. The illusion is real. Are you?
Monopole percieved, Monopole achieved.
Reply | Report Abuse | Link to thissleekmason:
Reply | Report Abuse | Link to thisYour language and arguments says a lot about you, obviously you have little understanding of science, if not you would be aware of one of the most important experiments in physics.
Should you want to know more here is a link:
http://www.nasa.gov/missions/highlights/launch_update_gpb.html
I am slightly impressed that you have the ability to comprehend that religion is bunk, but when you talk of karma and spirituality obviously you believe in a god. Karma is your future, which is predestined. Sorry I can not believe in that. Your ideas on infinity must stem from your belief in a god, so quite simply I am wasting my time on you.
I truly wish I was 22, not for any reason other than my mind would not be conditioned by education from the 1950s on.
I percieve both karma and spirituality to be manifestations of ethics in regards to others (karma), and ethics in regards to self( spirituality). No special deity needed/ At a higher level I would say the universe itself is an entity beyond our comprehension, and that we are simply manifestations.
Reply | Report Abuse | Link to thisMy appologies for being so rude in my post. I was an ass. I could have handled it differently.
My idea of infinity comes from logical thinking. Because I can continue to count forever both backwards, and forwards, I can clearly show a situation where infinity exists, even if our particular Universe is finite. Again, no special diety necessary.
Heres a link that refutes yours. No, I don't really believe it;) It all stops short of finality in his site. http://www.sjcrothers.plasmaresources.com/index.html
I have referred to your links and gone to other links from there but still find the concept of infinity mathematically and logically a problem.
Reply | Report Abuse | Link to thisMathematically positive and negative numbers are possible so where is -infinity, what about +infinity plus - infinity, zero X infinity another problem.
Logically sentient life forms that exist in time comprehend time. When no sentient life forms exist time is irrelevant, even if Einstein was wrong.
For me the existence of an event horizon is indication that black holes exist, which is disputed by Karl Schwarzschild.
From my not-learning but getting very high scores in Calculus (could solve all the exam questions, without understanding, much like a dumb computer) things tend to be infinite or tend to zero but never are.
We can never count to infinity, if the very first life form ever to exist was taught to count and kept counting till today, it would still be an infinity away from infinity.
Gravity may slow time, and black holes may stop it, but it takes sentient forms to comprehend it. Our consciousness seems to exist in an electro-chemical matrix generated by neurons, in which case our little sun could be sentient. Also read the black cloud by Fred Hoyle.