Super-Magnet Sheds Light on Semiconductors 64
Stony Stevenson writes "A group of researchers at Florida state have demonstrated a magnet design that could shed new light on nanoscience and semiconductor research. 'The Split Florida Helix magnet can direct and scatter laser light at a sample down the centre of the magnet and from four ports on the sides. Due to become fully operational in 2010, the device can generate fields above 25 tesla. The highest-field split magnet in the world currently attains 18 tesla ... The scientists will be able to expand the scope of their experimental approach, learning more about the intrinsic properties of materials by shining light on crystals from angles not previously available in such high magnetic fields.'"
Minor correction - it is Florida State... (Score:5, Informative)
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Magnets BENDING light beam?!?! (Score:4, Interesting)
How is magnetism able to affect a beam of light?
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Having said that... I came across this - http://www.wonderquest.com/extinctions-safetyglass-magnetslasers.htm [wonderquest.com] (Scroll down for pertinent info). Apparently "electromagnetic waves can bend light through an indirect, quantum effect--but to such a tiny degree that we cannot measure it." So, maybe bigger magnet = more bending = measurable?
Re:Magnets BENDING light beam?!?! (Score:5, Informative)
Light is not affected by magnetic (or electric) fields since photons are neutral (no charge). You cannot deflect light with a magnetic field alone (although applying magnetic or electric fields to some materials can alter their refractive index and thereby change the deflection of a light beam passing through that material).
The connection between "light" and "magnets" in this new work is actually that the team found a clever way to build a large (and powerful) magnet that has gaps in it. These ports allow laser light to be directed at a sample sitting in a very high electric field (and allow measurements of the light scattered from the sample).
While it may not seem to be a huge achievement to build a magnet with holes in it, you have to keep in mind that building a 25 T magnet is already a big challenge: doing it with the additional constraint that you want easy physical access to the region of maximum field strength is even harder. This new setup should allow for some cool experiments, since it can probe in real-time (using light) how materials behave under very high magnetic fields.
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Re:Magnets BENDING light beam?!?! (Score:5, Informative)
The reason photons are referred to as "electromagnetic radiation" is not because they are affected by EM fields, but because they are EM fields. The photon is the force carrying particle [wikipedia.org] for the electromagnetic force. What that means is that electric and magnetic fields are in fact "made of" photons: in quantum field theory, their action is in fact described by the exchange of virtual [wikipedia.org] photons.
Since electric and magnetic fields are carried by photons, it would make for a strange universe if the photon had an electric charge, and were affected by those fields. In effect, it would mean that the photon would couple to itself, leading to all kinds of strange effects, like rays of light bouncing off of each other or attracting each other (in vacuum). Such effects are not observed.
Notes:
1. As I mentioned before, it is possible for magnetic or electric fields to affect the propagation of a light ray indirectly through their action on a material. Light refracts through material interfaces because of differences in refractive index. For some materials, a magnetic or electric field can be used to modulate the refractive index, and thereby change the path a light ray takes through the material. But magnetic fields do not affect photons in vacuum.
2. Some theoretical work suggests that the action of extremely intense magnetic fields could polarize the virtual particles that exist in vacuum, and thereby slightly modify the effective vacuum refractive index. This would then be a case of a magnetic field affecting light. Such effects would only occur at massive field strengths (perhaps at the surface of a neutron star), and are as of yet experimentally unverified.
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Since electric and magnetic fields are carried by photons, it would make for a strange universe if the photon had an electric charge, and were affected by those fields. In effect, it would mean that the photon would couple to itself, leading to all kinds of strange effects, like rays of light bouncing off of each other or attracting each other (in vacuum). Such effects are not observed.
It is very true that those effects are not observed and that in the case of photons it would be a strange world. But, in the case of the strong interaction, the force is carried by gluons which do couple to themselves. And this does not lead to a strange Universe.
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Oh, and no light as we know it, since photons would be strictly limited to very short range interactions.
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Wow, does no one know that light is an electroMAGNETIC wave ????
Yes we do know that. We also know that this fact has nothing to do with the ability to bend light using magnetic fields. In the classical view, light is electromagnetic waves. From basic EM theory we know that two electromagnetic fields "crossing paths" will not change each other. If you don't trust me, go back to your introductory book on EM and do the math. In the world of quantum mechanics, light is a particle, photon, and are electrically neutral. Neutral particles are NOT affected by magnetic fields.
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Apparently you don't know that light has no charge so it cannot be bent by electric or magnetic fields.
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I guess you are right. Google is useful.
Oops, It's from the "John Titor" hoax.
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Electromagnetic radiation is a variation in the magnetic and electric fields. See superposition [kettering.edu], and note that EM radiation is made up of bosons [wikipedia.org].
The question was not a dumb one.
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From what I remember learning in physics class, light travelling perpendicularly through a magnetic field gets "twisted" (either CW or CCW, depending on the direction of the field and the direction light is coming from), changing polarity but not direction. So if you pass polarized light through a magnetic field, you'd have polarized light at a different angle coming out the other side. How much it twists depends on how much magnetic field strength it has to pass through (both volume and intensity).
I'
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The group I'm involved in is doing some work in applying the Faraday rotation effect :
http://jwtioh.bluesonic.net/files/04202947.pdf [bluesonic.net]
http://jwtioh.bluesonic.net/files/01704539.pdf [bluesonic.net]
So... (Score:5, Funny)
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Except noticing his limitations
Confusing Headline??!! (Score:5, Informative)
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As was pointed out this magnet is special becuase it will let researchers get laser light to their sample while it's in the high field.
For those that are wondering why high fields are useful for studying semiconductors, it's that one of the most important variables in the equasions governing semiconductors is Magnetic field divided by temperature.
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Layne
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Fully Operational... (Score:5, Funny)
NOW! Witness the power of this fully operational supermagnet!
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How to create your own Bermuda triangle in one easy step
Nanoscience and Semiconductors? Pfft. (Score:2, Funny)
Teslas (Score:5, Informative)
1 Tesla is about 20000 times the strength of the magnetic field on earth.
Those rare-earth magnets that move the head inside of a hard drive are about 1.25 T.
MRIs in hospitals use about 3 T.
16 T will levitate a frog.
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That's pretty useless. What about a gecko? Could I do that with 16T? Or even 12T?
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The researchers are getting on a bit so they are still using kermit and not mozilla.
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One thing that's really cool about this is its application in NMR. The reason for having such tiny little bores on those things and having them essentially inaccessible from the outside save for the tiny little hole in the top where the sample is dropped is that the goal is to have really high field homogeneity. If you can, for instance, get a field homogenous on the ppb level, then y
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Technical question (Score:2)
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How do they generate fields that strong? Huge amounts of current with some type of active cooling? I always wondered that.
They are basically "just" electromagnets: you pass a current through a loop of conducting material and it will generate a magnetic field around it (due to the movement of charge).
To make really powerful magnets, of course, you need to use some tricks, such as shaping the system to concentrate the field at a particular point. In machines like MRIs [wikipedia.org] and NMRs [wikipedia.org], the magnet is typically cooled (e.g. to liquid helium temperatures) which makes it superconducting. This allows a very large current to be passed thr
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Also depends on the frequency of operation; get high enough and the losses due to skin and proximity effects become unbearable (stuff like Litz wires and appropriate coil turns arrangement can help to mitigate this).
One more thing to worry apart with such high field
that's a powerful magnet (Score:3, Insightful)
capabilities (Score:1)
I would not wish to see the results (Score:2)
I would NOT want to see the result when even 1 was turned on.
Space propulsion yet? (Score:2)
Info on the split and other magnets (Score:3, Informative)
Metal Objects (Score:1)
I can see it now:
Sees metal piercings flying through the air.
Man with screws in the leg
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Such risks are already well known:
Look at the picture halfway down this article. [howstuffworks.com]