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Supercomputing Science

Super-Magnet Sheds Light on Semiconductors 64

Posted by Zonk from the throm-throm-throm dept.
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.'"
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Super-Magnet Sheds Light on Semiconductors More

Super-Magnet Sheds Light on Semiconductors

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  • Minor correction - it is Florida State... (Score:5, Informative)

    by BradySama ( 755082 ) on Friday November 02, 2007 @11:02AM (#21213023)
    More specifically, this happened at Florida State University's National High Magnetic Field Laboratory. Thanks!
    • Thank you for this important clarification. I highly recommend anyone visiting Tallahassee get a tour of this amazing lab!

  • Magnets BENDING light beam?!?! (Score:4, Interesting)

    by denis-The-menace ( 471988 ) on Friday November 02, 2007 @11:03AM (#21213041)
    Did I miss something in science class?
    How is magnetism able to affect a beam of light?

    • Re: (Score:2, Informative)

      by JCSoRocks ( 1142053 )
      disclaimer - I'm not a physicist.

      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)

      by kebes ( 861706 ) on Friday November 02, 2007 @11:14AM (#21213213) Journal
      No, you're right. The summary is just awkwardly worded.

      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.

      • Re: (Score:1, Troll)

        by IronWilliamCash ( 1078065 )

        No, you're right. The summary is just awkwardly worded. 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).
        Wow, does no one know that light is an electroMAGNETIC wave ????

        • Re:Magnets BENDING light beam?!?! (Score:5, Informative)

          by kebes ( 861706 ) on Friday November 02, 2007 @11:39AM (#21213611) Journal
          Yes, of course light is an electromagnetic wave. Light, like all forms of EM radiation (gamma rays, IR, radio waves, etc.) is carried by photons, which are elementary particles that have no electric charge. Since they have no electric charge, they are not affected by electric or magnetic fields.

          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.

          • 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.

            • Re: (Score:2)

              by ceoyoyo ( 59147 )
              I don't know... the strong force is pretty weird. For example, it gets stronger with distance, meaning that colour charged particles can never exist independently. If electromagnetism followed the same rules plasmas, ions and electric currents would be impossible. No stars, no ionic solutions (such as your blood or seawater), and no electricity.

              Oh, and no light as we know it, since photons would be strictly limited to very short range interactions.

        • Re: (Score:1, Informative)

          by Anonymous Coward

          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.

          • No they don't. The Lorentz force is F=q(E + vxB) (x represents vector product). q is the charge so a neutron will not experience any Lorentz force. Now, since neutrons consist of three quarks, each of the quarks will experience a force but on average the sum of the force will be zero.

        • Re: (Score:2)

          by ceoyoyo ( 59147 )
          Yes, so?

          Apparently you don't know that light has no charge so it cannot be bent by electric or magnetic fields.

      • Re: (Score:1, Informative)

        by Anonymous Coward
        The other thing is that experiments sometimes need a certain orientation of the magnetic field. So, if you're using a solenoid (which is what all the highest field magnets are made like), then it's no good sending laser light down the axis of the solenoid, because the field is then pointing either toward or away from the light pulse. Therefore you need a hole in the side of the solenoid, which is when it gets tricky, e.g. keeping the magnetic field quality good etc.

    • Re: (Score:2, Insightful)

      by jpfed ( 1095443 )
      To everyone that replied about how dumb the parent's question was:

      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.
    • Magnets don't affect a beam of light directly. The point is to put a sample in their, and the magnetic field changes the behavior of the sample, which you measure with a beam of light.

    • Re: (Score:2)

      by mark-t ( 151149 )

      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'

      • 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.
        Not in a vacuum. See Faraday rotation [wikipedia.org]
    • Dead easy. Magneto-optic effects (Faraday, Kerr, Zeeman, circular birefringence, etc.)
      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)

    by C0rinthian ( 770164 ) on Friday November 02, 2007 @11:10AM (#21213179)
    ...will Gordon Freeman be taking the samples into the test chamber?

    learning more about the intrinsic properties of materials by shining light on crystals from angles not previously available in such high magnetic fields.

  • Confusing Headline??!! (Score:5, Informative)

    by tonywestonuk ( 261622 ) on Friday November 02, 2007 @11:11AM (#21213191)
    From what I gather, this magnet isn't able to split/focus light, any more than lesser powered magnets. What makes this one different, is that usually, at such high fields, it is phisically imposible to get any sort of light inside, as the structure of the magnet has no gaps that can be used to shine a light in, ie, 100% enclosed. This magnet is constructed differently, in that even though it attains the highest magnetic fields, the insides are still viewable from outside, and so lasers/etc can be focused from the outside, onto the subject while its in operation.

    • The superconductive and resistive magnets at the National High Magnetic Field Lab are ussually a tube for the working area.

      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.

    • When they say "sheds light" they almost mean it literally too, not that the magnet is glowing, but that it allows for lasers to shine through it. (I.e. the magnet design allows lasers to shed light on the superconductor.) ;-)

  • Fully Operational... (Score:5, Funny)

    by Greyfox ( 87712 ) on Friday November 02, 2007 @11:17AM (#21213269) Homepage Journal
    Due to become fully operational in 2010, the device can generate fields above 25 tesla...

    NOW! Witness the power of this fully operational supermagnet!

  • According [209.85.165.104] to the locals down here in Tally, the Mag Lab changes the weather, causes (or suppresses) hurricanes, and makes airplanes fall from the sky!

  • Teslas (Score:5, Informative)

    by loafula ( 1080631 ) on Friday November 02, 2007 @11:28AM (#21213421)
    To put it into perspective:
    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.

    • Re: (Score:3, Informative)

      by bperkins ( 12056 )
      16T will not necessarily levitate a frog. It takes a certain magnetic field gradient to achieve this. This is typically done with magnets that produce about 16T, but it depends on the design of th magnet.

      • Re: (Score:2)

        by bgarcia ( 33222 )

        16T will not necessarily levitate a frog. It takes a certain magnetic field gradient to achieve this. This is typically done with magnets that produce about 16T
        In what part of the world do people typically levitate frogs?
    • > 16 T will levitate a frog.

      That's pretty useless. What about a gecko? Could I do that with 16T? Or even 12T?

      • Re: (Score:2)

        by dbIII ( 701233 )

        Frog ... That's pretty useless. What about a gecko?

        The researchers are getting on a bit so they are still using kermit and not mozilla.

    • Actually, the Earth's magnetic field is about 6 gauss and there are 10,000 gauss in a Tesla... So not quite 20,000 times.

      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

    • Yes indeed! The Force is strong in this one! ;)

    • Re: (Score:2)

      by l0b0 ( 803611 )
      Other interesting magnet & strengths [hypertextbook.com].
  • How do they generate fields that strong? Huge amounts of current with some type of active cooling? I always wondered that.

    • Re: (Score:3, Informative)

      by kebes ( 861706 )

      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

      • Re: (Score:2, Interesting)

        by WhoBeDaPlaya ( 984958 )
        In applications like MRI where you need not just high-intensity but also high-precision, you'll typically have a main superconducting coil and a couple of ancillary coils to iron out the kinks in the field pattern (eg. tesseral and shim coils).

        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
  • not only can it do these things to crystals, but it can also take a rather straightforward story summary, and twist it in such a way that it seems to imply that the magnet can bend light. that's a powerful magnet that can bend a story summary
  • Okay, so it can do all of that really cool stuff. But the real test is whether or not you can strap 4 to your hands and feet and climb up the walls. Only then will it be a groundbreaking design.
  • So can split helix magnets get us into space yet?

  • Info on the split and other magnets (Score:3, Informative)

    by ElGuapo2872 ( 1183509 ) on Friday November 02, 2007 @02:17PM (#21216051)
    The split magnet mentioned in this story is a purely resistive magnet. This means that it will operate at room temperature and uses copper alloy coils (pretty sure its a copper-silver allow) along with a tremendous amount of current to generate a magnetic field. The resistive magnets at the NHMFL operate at up to 60,000A and at up to 500V which equates to about 30MW. This amount of power is difficult to dissipate and makes these some of the worlds most powerful hot water heaters. The coil technoloy used is known as Florida-Bitter. The tricky part about a split magnet is that you have to take the most efficient portion of the magnet, which are the coils close to the center and effectively move them to the farthest region of the magnet. For comparison, the most powerful resistive magnet at the NHMFL with comperable parameters generates 35T. The most powerful persistant magnets however are the hybrids which have superconducting coils in the low field regions and resistive coils in the high field regions. The most powerful is 45T A lot more information can be found at: http://www.magnet.fsu.edu/ [fsu.edu]
  • Wonder what would happen when someone walks by with metal in their body?

    I can see it now:

    Sees metal piercings flying through the air.
    Man with screws in the leg .... what's that big circle thing over there .. whoa (as the screws flys from his body).

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