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Nanotechnology + Superconductivity = Spintronics 88

Posted by timothy
from the idea-whose-time-keeps-coming dept.
karvind writes "Spintronics is a nanoscale technology in which information is carried not by the electron's charge, as it is in conventional microchips, but by the electron's intrinsic spin and if a reliable way can be found to control and manipulate the spins spintronic devices could offer higher data processing speeds, lower electric consumption, and many other advantages over conventional chips--including, perhaps, the ability to carry out radically new quantum computations. PhysOrg is reporting that University of Notre Dame physicist Boldizsar Janko and his colleagues have found a way to achieve this control using a magnetic semiconductor, insulator and superconducting material stack of thicknesses of order of few dozen nanometers. IBM and Stanford are also looking into spintronics."
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Nanotechnology + Superconductivity = Spintronics

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  • by Silverlancer (786390) on Saturday May 07, 2005 @08:45PM (#12465055)
    Seems like one of the Unsolved Problems in Physics [wikipedia.org] isn't exactly unsolved anymore.
    • by Rosco P. Coltrane (209368) on Saturday May 07, 2005 @08:57PM (#12465106)
      Seems like one of the Unsolved Problems in Physics isn't exactly unsolved anymore.

      Re-read TFA where it says "Boldizsar Janko and his colleagues believe they have found such a control technique" and "Although Janko and his colleagues have tested their approach so far only through computer simulations".

      Not exactly a practical, demonstrated technology yet. Wikipedia is therefore current.
    • That's been unsolved for years now, eg the read head in your hard disk uses GMR, which is a spintronic effect.

      The wikipedia article is probably referring to the specific ability to make a selective filter to pass/block currents of only a specific spin type. Or to make a transistor to amplify/switch only on a specific spin type. etc.

  • by EtherAlchemist (789180) on Saturday May 07, 2005 @08:46PM (#12465058)

    Are you SURE this isn't a technology developed jointly by the press and the White House?
  • by AthenianGadfly (798721) on Saturday May 07, 2005 @08:47PM (#12465067)
    Microsoft is reportedly already somewhat advanced in spintronics. A company offical reportedly said "We consider ourselves to be industry leaders when it comes to manipulation using spin."
  • DIY? (Score:2, Funny)

    by Doc Ruby (173196)
    What's the cheapest device that I, a layman, can buy to set the spin of large amounts of electrons (several coulombs per second) to a certain value?
    • You could buy anything and start spinning it around, but I'm pretty sure that's not what you had in mind.
      • by Decaff (42676)
        You could buy anything and start spinning it around, but I'm pretty sure that's not what you had in mind.

        Interestingly.... no!

        The electron 'spin' being discussed is a quantum mechanical property and is not the same as macroscopic rotation.
    • Re:DIY? (Score:4, Funny)

      by Rosco P. Coltrane (209368) on Saturday May 07, 2005 @08:53PM (#12465089)
      What's the cheapest device that I, a layman, can buy to set the spin of large amounts of electrons

      A fridge magnet.

      (several coulombs per second) to a certain value?

      A very big, precisely calibrated fridge magnet.
      • Isn't there a difference in energy between the spin states? Am I not going to need to keep the fridge (or its radiator) coupled to that magnet?
        • Re:DIY? (Score:3, Informative)

          by DarkMan (32280)

          Isn't there a difference in energy between the spin states?

          Not normally, no, in general.

          You can find some situations where there is a difference in the energy between the two states. The most common one is the application of a magnetic field - then, the spin state that is most aligned to the field is favoured over the other one.

          The other major case is in chemcial species that have partially filled orbitals. Most of these tend to have a net magnetic moment anyway, but are much more complex, and les

        • Am I not going to need to keep the fridge (or its radiator) coupled to that magnet?

          The fridge is unimportant. It's the magnet that's going to affect the electron spin. The parent didn't emphasize enough that you would need a big magnet.

          Not big in the sense of "Damn, this sucker is heavy." Big in the sense of "Holy Shit! I need an industrial electrical feed into my house? I need liquid nitrogen and maybe even liquid helium? Why is every piece of steel within 20 m of my magnet flying toward it at frighte

          • Not quite that big. I use one of these- typically very strong, but field falls off rapidly (1/r or 1/r^2), so shit doesn't fly into the magnet till you get within at least 2-3 meters of it (typically 1-1.5m). And you only need the big current once- the reason you use liquid nitrogen and helium is to cool your magnet to temperatures at which the material it's made of will superconduct. Put current in now, keep your magnet cool, and you no longer have to be tied into the grid- the current just keeps circli
        • Re:DIY? (Score:3, Informative)

          by Quantum Fizz (860218)
          Isn't there a difference in energy between the spin states?

          For free electrons there is only an energy difference in the presence of a magnetic field.

          For atoms, an energy difference comes about from Zeeman splitting, which can be seen by standard textbook perturbation theory of the hydrogen atom in a magnetic field, where the otherwise degenerate levels split. This Zeeman splitting is how astronomers are able to detect the magnetic fields of astronomic objects.

          Can you explain exactly what you are

          • Re:DIY? (Score:3, Informative)

            by Doc Ruby (173196)
            I thought that the 2 different spin states had different energies. So setting the spin states of lots of electrons to the higher energy one could store energy. Later reversal of the states would release that energy (possibly minus some quantum mechanical inefficiency). A battery of such "spun" electrons might have greater storage capacity than one storing merely charged electrons. But if the energy states are the same, and the spins of a population aren't conserved, then the whole idea is wrong.
            • Re:DIY? (Score:3, Insightful)

              by Quantum Fizz (860218)
              Okay, if you want to get technical you have to look at the Hamiltonian [wikipedia.org] of the problem, to see the change of energy would be to flip a single spin.

              Free electrons means without any other interactions, and spin up and spin down have no preference. In fact, the directions up/down don't mean anything unless some non-isotropic disturbance is present in the system. This would usually be the applied magnetic field.

              If you have a ferromagnet, the electrons want to align parallel, so flipping one electron costs

              • Just when it looked like this (probably poorly constructed) idea was lost on an (even more clueless than me) Slashdot, I get an expert :).

                I didn't realize that the electron spin direction was the same phenomenon as the orientation of the magnetic field - is that correct? If lots of "up" electrons are conducted through a "down" permanent magnet, does that change the orientation of either the electrons or magnet, or is there potential energy in the up electrons in the down field? If the latter, does that ene
                • Re:DIY? (Score:4, Informative)

                  by Quantum Fizz (860218) on Sunday May 08, 2005 @12:47AM (#12466048)
                  Electron spin is NOT the same phenomenon as orientation of magnetic field. But you can think of it the following way. An electron is a tiny magnetic dipole. The potential energy of a dipole in a magnetic field is the inner product -mu dot B. Where mu is the dipole moment (Bohr Magneton in the case of an electron), B is the magnetic field. The dipole wants to go to the lowest energy state, which is aligned with the field (negative energy).

                  Quantum mechanics forces a measure of the electron's spin (and hence the direction of the dipole moment) into one of the allowable eigenstates. For a spin-1/2 fermion, such as an electron, there are only two states.

                  now - if you apply a field in the z direction and measure the spin in the z direction, there is a definite preference for the spin to align with the field.

                  if you apply the field in the y direction and measure in the z direction, then both states are of equal energies and there is no preference.

                  If you turn on interactions between electrons, like ferromagnetic or anti-ferromagnetic coupling, you get interesting effects, esecially at points where there the electron-electron interaction is countered by the field, and you have phase transitions at that point. if you allow for different couplings, different field directions, you can build up very rich phase diagrams of such systems, which are actually being studied by top physicists today.

                  Eg - anti-ferromagnetic interactions (neighbors want to be anti-aligned) on a triangle lattice is a frustrated magnet. A spin will be up, another neighbor will be down, the third is equally frustrated and doesn't know where to go. This makes very degenerate ground states, which have interesting properties.

                • Re:DIY? (Score:2, Informative)

                  by Stephen H-B (771203)
                  O.K., first things first. IAAC but IANAP so I can't give you the exact formulae. The 'spin' of an electron is not so much the electron spinning on an axis so much as a term used to describe the direction of its quantum magnetic moment.

                  Electrons placed in a magnetic field will have a potential difference between the populations aligned with and against the field, but the difference is so small that the applications at this point are severely limited.

                  The population difference in a 5 tesla field (the kind you

    • Re:DIY? (Score:5, Informative)

      by Quantum Fizz (860218) on Saturday May 07, 2005 @09:02PM (#12465129)
      What's the cheapest device that I, a layman, can buy to set the spin of large amounts of electrons (several coulombs per second) to a certain value?

      Here's a semi-serious reply to your obviously tongue-in-cheek question. I'll assume by 'certain value' you mean direction, since the total spin of an electron is fixed to hbar/2.

      It depends how many spins you want to align, what percentage of the total number of spins you want to align, and how accurately you want to control the direction the spins are aligned to. In a nutshell a magnet will align the spins, cooling will also align the spins (for ferromagnets and antiferromagnets). doing both will do it faster and give more control. But that adds to the cost.

      At absolute zero the slightest applied magnetic field to a paramagnetic system will line the spins entirely along the direction of the applied field.

      If you get a ferromagnet, you only need to cool below the curie point and then apply a field to get the spins aligned. You'll need to go to a stronger field than above to overcome the hysteresis, though.

      As someone said above, a simple refrigerator magnetic will put out weak-enough fields that will allow you to align several spins, and it will have an effect on coulombs per second if you move it fast enough. Not to high degree of polarization, but enough to attract the magnet to the refrigerator, so that should answer your question.

      • Well, it's pretty close to answering my (serious) question. If my electric generator produces 15A, and I want to charge a bank of batteries with 1MC of electrons, all of which have their spin set to "up, can I do that by wrapping a fridge magnet around the charging cable?
        • Re:DIY? (Score:3, Informative)

          by Quantum Fizz (860218)
          I'm confused what you're trying to do. Charging and aligning spins are two separate things. If you have a spintronic charging unit, which is what you're proposing, then you can do that, but such an object is the main point of all this research in the first place.

          If you want to send a 100% polarized current of spin-up electrons into your batteries, your batteris will have a horrible coherence time and you'll eventually lose the coherence. Ie, after probably a few seconds any free electrons chosen at ran

  • by Ledneh (673693) <ledneh AT radix-lecti DOT net> on Saturday May 07, 2005 @08:49PM (#12465073) Homepage
    I know this isn't exactly what the article said, but I had a thought. If computers could base data on spin and charge at the same time (4 possibilities), would there be any significant advantage to being able to work natively in base 4 instead of base 2?
    • Actually, would it be base 3 or 4? Bah, I'm clearly a little brain fried. -_-
      • Memory now doesn't use positive and negative charge, it already uses magnetic fields. So it will still be binary, spin up and spin down.
        • I think he's talking about the CPU, in which case each 'transistor' instead of working with presence/absence of charge would operate on the four following states : no charge, only spin up electrons, only spin down electrons, both spin up and spin down electrons. Such a device might be able to switch based on these four states as quickly as current MOSFET's switch on spin-independent voltages.
          • Ah yes, that makes some sense. Basically you have an SET where the tunneling probability into the island changes on the island's occupancy. If a spin up electron is present, then a spin up electron will have a harder time tunneling than a spin down. At least that's what springs to my mind. Thanks for the clarification.

    • No, it woudl still be base 2, because of the logic behind computing. We might represent multipule bits per electron, or even entire bytes, but Things would still in the end be base 2, spin up or spin down.
      • No, not if the four basis states are no electrons, spin up electrons, spin down electrons, and both kinds of electrons.

        Base four is nice because many hardware/software algorithms can be used since groups of two bits have 4 states, and a base-4 'bit' can be thought of as two independent bits.

    • It worked for DNA, who can argue with that?
  • How does Spintronics stack up against Plasmonics? I mean, they're both being touted as The Next Big Thing in chips. Are the compatible in any way? Different time frames?
  • I heard of spintronics before. I have some idea of what electron spin is from university, but not much more. So when I saw the article, I thought "wow, great, a nice-looking /. blurb choke full of links to the subject"... only to discover that 4 out of the 5 links link back to /. itself, and the last one links to a half-page semi-general article in physorg.com.

    I don't know, I guess I may as well Google spintronics at random...
    • by Quantum Fizz (860218) on Saturday May 07, 2005 @09:19PM (#12465204)
      Spin is usually called "intrinsic angular momentum". Basically it's an angular momentum that's always present in all elementary particles, and is quantized in units of hbar/2.

      Particles with integer spin, such as phonons (spin 0), photons (spin 1), gravitons (spin 2) are called Bosons and obey Bose-Einstein statistics. Any number of bosons can be found in any quantum state, and at low temperatures they can condense into the ground state via Bose-Einstein Condensation.

      Particles with half-integer spin, such as electrons, protons, neutrons (all spin 1/2) are called Fermions, and obey Fermi-Dirac statistics. This means interchanging two fermions in a system will cause the wavefunction of the system to acquire a factor of negative one. So if two fermions are in the same quantum state, that component of the wavefunction must be equal to it's negative - meaning zero. This is the Pauli Exclusion Principle, meaning no two fermions can ever exist in the same quantum state of a system. This effect has profound impact on physics, accounting for orbital nature of atoms, band structure of semiconductors, etc.

      Anyway, back to your question about spin, another aspect of spin is that the allowable spin values must differ by integer units of hbar. So electrons, with total spin of hbar/2 are allowed two states that differ by hbar - +hbar/2 and -hbar/2. Usually the direction is chosen by an applied field, or whatever direction is chosen to measure the electron spin.

      Spin is tricky because it isn't simply additive, but follows appropriate group theory. Electrons are part of SU(2) algebra, and spin interactions are weird. For example, you can simultaneously know the total spin (electrons are always hbar/2) and the spin component along one direction (for electrons this could be +hbar/2 and -hbar/2). But you cannot know the x, y, and z components simultaneously, basically because the Pauli matrices don't commute (Heisenberg uncertainty principle). So in actuality a spin-up electron really points somewhere along a cone that mostly points up, but you don't know more than that.

      With two electrons, you can simultaneously know EITHER the total spin of the pair AND the total spin projected along one axis, OR you can know the projections of the two independent spins along one axis. If one electron is up and another is down, the system is in a state of 1/sqrt(2) (spin-Zero + spin-One). Also - this means that the two-electron system can exist in a Spin-1 state with the spin in one direction zero, or a Spin-0 also with the spin in one direction zero. Since the two electrons would have an integral number of spin, the system acts like a Boson. This is what allows superconductors, which are mentioned in TFA, to pair up and effectively condense.

      Additionally, the spin-zero state of two electronss is very important in quantum communication, quantum teleportation, and quantum computation. This is the state with total spin zero, so no matter what direction you measure one spin, the other spin is aligned opposite.

      • by radtea (464814)
        Additionally, the spin-zero state of two electronss is very important in quantum communication, quantum teleportation, and quantum computation. This is the state with total spin zero, so no matter what direction you measure one spin, the other spin is aligned opposite.

        Oddly enough, free electrons do not have well-defined spin directions (interference phenomena destroy any possibility of measuring it, so it does not exist). Because of this it is not the case that electron-spin correlation is important to
    • by karvind (833059)
      Quick Google search and few links which have more detail:

      Scientific American [sciam.com] (warning: loaded with ads etc)

      Not for the light-hearted, a thorough review in Reviews of Modern Physics [aip.org] (subscription required, if you cannot access the article, drop me an email at karvind@NOSPAM.gmail.com)

      On Ferroelectric spintronics [colossalstorage.net] from Colossal Storage.

      Spintronics and Quantum Dots [unibas.ch]. Discussion about one possible implementation.

      Another good introduction [aist.go.jp].

      Hope it helps.

  • Lots of research (Score:5, Informative)

    by Quantum Fizz (860218) on Saturday May 07, 2005 @08:53PM (#12465094)
    Spintronics has been around for several years now, this project mentioned is really just one of many research projects, maybe the researcher Janko has friends with PhysOrg, or PhysOrg just picked him out of a hat.

    Spintronics also represents one of the quickest transitions from lab to market, next to the transistor via GMR sensors. The hard disk read heads on the hard drives in your computer, if you bought a new disk in the past few years, already incorporates spintronic effects through GMR (Giant MagnetoResistance). Most major media storage and also electronics companies have been heavily investigating spintronics for years too, not to mention a good percentage of condensed-matter physicsists, electrical and materials-science engineers.

    Spintronics is also being investigated for quantum computation because the two electron eigenstates in any direction (up / down) can make a good basis for the Zero and One states of a qubit.

    But to repeat the hype, spintronics does have potential to revolutionize the electronics industry by offering a whole new degree of freedom to manipulate of the electrons. 'Classical' transistors move/detect/switch charge, adding spin to the picture allows much more flexibility, and probably higher device speeds or data densities. Eg, perhaps microprocessors can go from binary as presence/lack of charge to spintronic up/down charge. Or perhaps even base-4 using presence/absence of both spin up and spin down flavors of electrons.

    • "Or perhaps even base-4 using presence/absence of both spin up and spin down flavors of electrons."

      I believe it was proven (sorry I don't have the source...) that the most efficient base to compute with is e, or 2.718... Since that has no physical interpretation at this time (how do you have a fraction of a state?), the next best number to use is 3 (trinary), simply because that is closer to 2.718 than 2 (binary).

  • I carry the cables for his spintronics! Ya gotta believe me!
  • ArfArfArf is a nanoscale technology in which information is carried not by the electron's charge, as it is in conventional microchips, but by the BowWowWow and if a reliable way can be found to control and manipulate the BowWow effect, ArfArfArf devices could offer higher data processing speeds, lower electric consumption, and many other advantages over conventional chips--including, perhaps, the ability to carry out radically new quantum computations, cure baldness, relieve users of the heartbreaks of ecze
    • Science publications only really profit if done in respected peer-reviewed journals. In the research world, PhysOrg and the like don't mean much for getting funding.
      • You retard RTFA:

        Now, University of Notre Dame physicist Boldizsar Janko and his colleagues believe they have found such a control technique. Their work, funded by the National Science Foundation through a Nanoscale Interdisciplinary Research Team grant, was published in the March 5, 2005, edition of the journal Nature.

        I work in a biochemistry lab and if you can get a publication in one of the two most highly ranked journals Science or Nature, it helps you greatly in getting funding (as they have from
        • You retard RTFA:

          Nice way to demonstrate your maturity. Makes me wonder if it's worth the time to bother replying to you.

          Anyway, I did RTFA, and was responding to the parent's claim (or overextended southpark joke) that merely mentioning a bunch of trendy technobabble words in PhysOrg implies profit. That's why I specifically referred to "real" peer-reviewed journals.

  • Hmmm... I seem to remember this...but I can't find record of it on slashdot. can anyone remember if this has come up somewhere before?

    .
    -shpoffo
  • Is it too late? (Score:3, Insightful)

    by BorgCopyeditor (590345) on Saturday May 07, 2005 @09:39PM (#12465269)
    As someone who reads Greek, I have a special reaction to words made up of in-themselves-meaningless fragments of Greek words: I cringe.

    Is it too late to stop the proliferation of "-tron" words? "-tron" means nothing; "electrons" are so called because of the Greek word for amber, which the Greeks knew to be capable of producing a static charge. What if people abstracted part of that word out and started calling every new technology "something-ber"?

    I think the technical name for the combining from "-tron" is a "cranberry morpheme," from "*cran," which apparently has no independent meaning.

    • Re:Is it too late? (Score:5, Informative)

      by Quantum Fizz (860218) on Saturday May 07, 2005 @10:33PM (#12465549)
      Too late, quantum physics has long ago settled on the suffix 'on' for representing discrete quanta of various excitations. Eg - photons, phonons, magnons, ripplons, gravitons, inflatons, solitons, instantons, etc. Although that actually has nothing to do with spintronics, but your post made me think of it.

      Of course the buzzword 'spintronics' is is just 'electronics' with the word spin substituted in. The actual less-trendy synonym for spintronics is Magnetoelectronics, which is what it's usually referred to in the "real" science journals, not popular outlets like PhysOrg. magnetoelectronics.

      BTW - since you mention Greek I thought a better example would be using the suffix Thon, as from Marathon, to refer to any excessivly long activity. Eg Bowl-a-thon, Dance-a-thon, Phone-a-thon, etc.

    • people eat cheeseburgers too... deal with it... I'm sure the awesome for real real greek you know had them takeing words from other langages and chopping them up as well.
    • As someone who reads Greek, I have a special reaction to words made up of in-themselves-meaningless fragments of Greek words: I cringe.

      Why? The -tron (or more accurately the -on suffix) words aren't Greek. They serve a useful purpose and the suffix is used in a single fairly well-defined way. I find it to be an ingenious solution to the labeling of particle-like objects.

  • by Gilmoure (18428)
    Scranton is sent skyward? [technovelgy.com]

    And what about cities down in Florida, like Lutz or Bithlo? Is there anyone down here who'd mind them being sent out into space?
  • In the next 50 years or so do you think that photonics or spintronics will become the main technology behind computation, or will we see a hybrid computer that uses the best of both technologies (e.g. computation/cpu using spintronics and data transport in buses between devices/peripherals using photonics)?
    • Seeing as I seem to work with photonics, I'll say that's the way to go.

      In reality, I bet it will be a combination of the two. Photons have spin 1 and as others have pointed out and electrons are +-1/2 spin. I wonder if stimulating a photon out of an electron spin state change could be used as a direct interface between the two technologies?

  • ...Nanotechnology + Superconductivity = Supertechnonanocondoexpialidocious
  • it has already imagined a beowolf cluster of itself!
  • Have a look at some of the google ads that appear around the article : ) "Life-prolonging magnets" "Immortality device".... : )
  • Spin Wave technology is nothing new, for that matter it's just it's nature,and then we "doscovery" it as something new. Check out: http://www.hightechscience.org/spin_wave_technolog y.htm [hightechscience.org]
  • For those interested in Spintronics and Quantum Entanglement visit this website.

    http://colossalstorage.net/ [colossalstorage.net]

You have a tendency to feel you are superior to most computers.

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