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Power Science

"Spin Battery" Effect Discovered 234

Posted by kdawson
from the usual-caveats-apply dept.
An anonymous reader writes "Researchers at the University of Miami and at the Universities of Tokyo and Tohoku, in Japan, have discovered a spin battery effect: the ability to store energy into the magnetic spin of a material and to later extract that energy as electricity, without a chemical reaction. The researchers have built an actual device to demonstrate the effect that has a diameter about that of a human hair. This is a potentially game-changing discovery that could affect battery and other technologies. Quoting: Although the actual device... cannot even light up an LED..., the energy that might be stored in this way could potentially run a car for miles. The possibilities are endless, Barnes said.'"
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"Spin Battery" Effect Discovered

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  • Cool. (Score:5, Funny)

    by B5_geek (638928) on Friday March 13, 2009 @10:23AM (#27181103)

    This sounds cool, but what they are not telling you is that it will stop working if you bring it south of the equator. :)

    • Re:Cool. (Score:4, Funny)

      by Anonymous Coward on Friday March 13, 2009 @10:24AM (#27181121)
      Yes, but on the other hand, it provides limitless energy in Washington DC!
      • Re: (Score:3, Funny)

        by jellomizer (103300)

        I bet it will even work on the O'Rily Factor even though he says it wont.

        • by zuzulo (136299)

          So you are saying this is essentially a magnetic flux capacitor?

          1985 here I come. ;-)

      • EMP (Score:3, Interesting)

        by mrops (927562)

        Article describes that nano-magnets apply a large magnetic field to "wound-up" the spin-battery.

        Having charged the hypothetical battery the article claims, the one that can run a car for miles. It is possible to discharge this battery near instantaneously, that should theoretically generate an EMP without a nuke. Something the military would be interested in.

        Off to patent my idea now.

        • Re: (Score:3, Funny)

          by Tony Hoyle (11698) *

          That would make a very nasty 'oops' whilst fiddling with your car... 'oops I just fried every electronic device for 5 miles!'

    • by spooje (582773)
      It'll still work, but you can only drive in a counter-clockwise direction.
    • Re: (Score:2, Funny)

      by eric2hill (33085)

      No, you just have to take the battery out and flip it around. The poles reverse south of the equator.

    • Why An LED... (Score:3, Insightful)

      by LEX LETHAL (859141)

      At least for the proof of concept stage, they might want to make a light source that consumes significantly less juice than an LED, and has a greater tolerance for fluctuation.

      From Wikipedia:

      "LEDs must be supplied with the voltage above the threshold and a current below the rating. This can involve series resistors or current-regulated power supplies." http://en.wikipedia.org/wiki/Led#Disadvantages [wikipedia.org]

      Using an LED as an example of what this tiny power souce can't power seems futile at this point.

      • Re: (Score:3, Informative)

        by fatboy (6851)

        I don't know of any common light sources that are more efficient than LEDs.

        I don't think you understand the meaning of that Wikipedia quote.

        The Voltage "above the threshold" means the voltage to cause the NP junction to conduct. In most diodes, that is .7 volts.

        The part about "a current below the rating", means that if you present enough voltage across the PN junction, as to reach the current limit of the PN junction, it will fail.

    • by Anonymous Coward

      I for one welcome the new SI unit human hair diameter overlord.

    • This sounds cool, but what they are not telling you is that it will stop working if you bring it south of the equator. :)

      It doesn't stop per-se, it just reverses polarity.

    • by frieko (855745)
      No problem. New Zealanders use wizardry to make electricity, and Aussies haven't discovered it yet.
  • Can't light an LED (Score:5, Interesting)

    by Taibhsear (1286214) on Friday March 13, 2009 @10:23AM (#27181109)

    Is this due to the scale of the device/experiment or is it a limitation in the output that they can get it to generate so far?

    • by Anonymous Coward on Friday March 13, 2009 @10:27AM (#27181167)

      Well the device they've built has the diameter of a human hair it doesn't really matter (unless it's also really really long). Ten thousand in a battery the size of a AA would surely give off more energy than existing alkali or NiMH batteries of the same size.

    • by BillOfThePecosKind (1140837) on Friday March 13, 2009 @10:33AM (#27181283)
      I would think it would be a limitation of the test size. If it's like any other electrical device, we should be able to stack a WHOLE bunch of them in series to create larger voltages. I really hope this goes somewhere, a lot of what is holding us back from implementing more renewable energy sources is the fact that we have no efficient (cost efficient mostly) way of storing the energy.
      • Re: (Score:2, Interesting)

        by poetmatt (793785)

        Well, it's potentially far more efficient than other current methods but how far is to be determined. Magnetic charges do not tend to hold forever, and are limited by certain mechanical aspects that can make it more difficult to harness long term too.

        However, both of those are just small engineering issues and should be things that can be resolved through working out the magnetics.

        • by Chyeld (713439) <chyeld.gmail@com> on Friday March 13, 2009 @10:54AM (#27181615)

          More importantly, you can stack several chemical batteries together for more power and the only issue you have to worry about is heat.

          Stack several magnetic based batteries together, are you going to have to worry about their fields interfering with each other? What if this is only a workable model when the battery IS the width of a human hair.

          • Re: (Score:2, Interesting)

            Hmmm, that is a very good point. Assuming those objects have a hysteresis curve like any non-permanent magnet you would have to be careful about how you put them together. Maybe there is a way they can "wind" the strands around a core to negate any potential field problems, kind of like how interleaving windings on an inductor can help with copper loss. All things considered, sounds like a fun experiment!
        • by GooberToo (74388)

          I wonder if wind turbines might be able to use this method to store "over charges produced from gusts which can then be feed into the grid when the wind drops off. In other words, simply use it as a capacitor for off-peak wind capacity.

  • Miles? (Score:5, Funny)

    by noundi (1044080) on Friday March 13, 2009 @10:25AM (#27181155)

    ...the energy that might be stored in this way could potentially run a car for miles. The possibilities are endless, Barnes said.

    Awesome, I have yet to travel miles by car.

    • Re:Miles? (Score:5, Insightful)

      by quickOnTheUptake (1450889) on Friday March 13, 2009 @10:46AM (#27181493)

      Although the actual device... cannot even light up an LED..., the energy that might be stored in this way could potentially run a car for miles.

      This is one of the least informative lines ever included in a tech summary.
      Any energy storing tech that's worth it's salt can potentially run a car for miles. It's a question of efficiency and cost. I can potentially power a car for miles with twisted up rubberbands if I want to, but that isn't a breakthrough in the field.
      And of course "miles" tells nothing. Powering a car 3-5 miles is next to worthless. If they said 10's of miles we would know this had the potential to replace current tech or at least come close. If they said 100's of miles we would be facing a revolutionary improvement.

    • All you'd have to do to make personal electric transport a realistic proposition, is set up a national network of filling stations where you could recharge those hair-thin devices [wordpress.com].

    • Scientists think that with a few modifications the new technology could work with kilometres too, though it would still be recommended that the host country is a monarchy or at least a strongly-presidental republic.

      Other technical difficulties like the extremely strong gyroscopic effect should be overcome as well.
  • by 140Mandak262Jamuna (970587) on Friday March 13, 2009 @10:26AM (#27181159) Journal
    Oh, yeah. We know how the spin works. But it works only in the PR side of things.
    • Re: (Score:2, Funny)

      by Anonymous Coward

      I think this actually solves the ancient gnome riddle:
      1. Create tiny stackable PR agent.
      2. Release photo of it's employer doing coke of a hookers ass.
      3. Harvest spin energy.
      4. Profit!

      • Re: (Score:2, Funny)

        by Anonymous Coward

        2. Release photo of it's employer doing coke of a hookers ass.

        Hey jerry, get back to work. Also, I told you to get rid of that picture.

    • by JosKarith (757063)
      Energy from spin... maybe we've found a use for our surfeit of politicians after all...
  • Achem (Score:4, Insightful)

    by girlintraining (1395911) on Friday March 13, 2009 @10:27AM (#27181163)

    In THIS house, we obey the laws of thermodynamics. So you create a magnetic field, okay. Great. What's to prevent everything that's metallic in the area from moving around it, inducing current in it, and converting it into useless thermal energy? In other words -- what's preventing the battery from discharging? It might be good for a really high-capacity capacitor, but a battery? Batteries are long term.

    • Re:Achem (Score:4, Insightful)

      by Eternauta3k (680157) on Friday March 13, 2009 @10:31AM (#27181239) Homepage Journal
      This is magic (a.k.a. science you shouldn't be hand-waving about)
    • Magnetic shielding?

      A Faraday cage?

      • Re:Achem (Score:5, Informative)

        by Hordeking (1237940) on Friday March 13, 2009 @10:37AM (#27181355)

        Magnetic shielding?

        A Faraday cage?

        Faraday cages don't stop magnetic fields.

        Even if you do stop the magnetic field (it can be done, but not with a Faraday cage), your battery would be inducing regular and eddy currents in the shield, which will convert the magnetic field to useless thermal energy over time.

        • Re:Achem (Score:4, Funny)

          by CecilPL (1258010) on Friday March 13, 2009 @11:01AM (#27181727)
          Now Eddy's in currents too? I think I saw his couch float by back when he was in the space-time continuum.
          • Now Eddy's in currents too? I think I saw his couch float by back when he was in the space-time continuum.

            I knew that Eddy kid was no good when he said he didn't like his teddy.

        • Re:Achem (Score:4, Insightful)

          by LordKronos (470910) on Friday March 13, 2009 @11:04AM (#27181797) Homepage

          Yeah, but what sort of time scale are we talking about? Even current batteries discharge themselves over time.

          • Yeah, but what sort of time scale are we talking about? Even current batteries discharge themselves over time.

            Batteries can't discharge very quickly because chemical reactions take time to release their stored energy. If it's not a chemical reaction, then it's likely that the release of energy can happen very quickly, if not close to instantly -- like a capacitor. And while a capacitor can store a charge for several days, batteries can store their charge for several years.

        • Re: (Score:3, Interesting)

          by davolfman (1245316)
          Mu metal?
          • Mu metal?

            That's the stuff. Of course, I suspect it works similarly to an electrostatic metal shell. An outside magnetic field induces a magnetic flux in the mu-metal shell, attenuating the field inside. Of course, this is likely to generate heat as the magnetic field tries to perform work on the shell.

            I could be wrong. I didn't really study magnetism very much.

    • Re:Achem (Score:5, Insightful)

      by Anonymous Coward on Friday March 13, 2009 @10:46AM (#27181497)

      Yeah you're right. I bet they totally never thought of that.

      When did "In THIS house, we obey the laws of thermodynamics" turn into some goddamn meme that gets pulled out when what you really mean is "I don't understand, can anyone please explain?"

      Because you're implying that these researchers are in some other house that doesn't obey the laws of physics, and that pointing this out is some revelation. Physicists from three institutions in two countries worked on this - are you really so stupid to think they don't know about thermodynamics? Really?

      • by Chyeld (713439)

        Regardless of whether the researchers understand what is going on, the question is whether the project itself is being presented with that understanding. It wouldn't be the first or last time a researcher presented what were ulitmately "useless in the real world" findings with the full internal knowledge that they would prove as such, simply to secure more grant money.

        Nor would it be the first or last time a wild eyed science journalist took a small breakthrough and extrapolated men on mars with jetpacks fr

      • Re:Achem (Score:5, Informative)

        by Comboman (895500) on Friday March 13, 2009 @11:17AM (#27182025)
        When did "In THIS house, we obey the laws of thermodynamics" turn into some goddamn meme

        Simpsons season 6, episode 21 ("The PTA Disbands").

      • Re:Achem (Score:4, Insightful)

        by girlintraining (1395911) on Friday March 13, 2009 @12:11PM (#27182855)

        Because you're implying that these researchers are in some other house that doesn't obey the laws of physics, and that pointing this out is some revelation. Physicists from three institutions in two countries worked on this - are you really so stupid to think they don't know about thermodynamics? Really?

        There has been a lot of crap science put forward over the years -- that debacle with cold fusion being foremost in my mind. But research has been faked in every scientific field and in some cases hasn't been revealed for decades. Very smart people can make very elaborate ruses. I may not be a group of physicists from three institutions and in two countries, but I'm not an idiot either and I resent your implication that simply because I use an internet meme that cancels my original question. And of all the fields of science that have had faked research -- an awful lot of it has been over magnetism. Perpetual motion machines, in particular -- their inventors love using magnetism. So my skepticism is quite justified.

        You still haven't addressed the point of my post: Which is how does a device that stores an electrical charge (a battery) via magnetism not go dead based simply on inductive coupling with nearby metals?

        • by Richy_T (111409)

          It doesn't even need nearby metals. I haven't RTFAed but this sounds like NMR effects where the energy extractable from the spin can be lost due to interactions with other fields (from other spins for example) and inhomogeneities in the magnetic field. It's been a while since I did any work on it but T1, T2 and T2* spring to mind.

        • Re: (Score:3, Informative)

          by mbkennel (97636)

          "Which is how does a device that stores an electrical charge (a battery) via magnetism not go dead based simply on inductive coupling with nearby metals?"

          Firstly, inductive coupling requires time dependent magnetic fields and probably realistically macroscopically reinforcing ones so that the field strength is appreciable at a distance.

          And then it could be locally thermodynamically stable, like opposing domains on a ferromagnetic surface, like a hard drive.

          Hard drives wont to spontaneously erase themselves

    • Re:Achem (Score:5, Funny)

      by Rogerborg (306625) on Friday March 13, 2009 @10:54AM (#27181619) Homepage

      In other words -- what's preventing the battery from discharging?

      A liberal coating of snake oil.

    • Re:Achem (Score:5, Informative)

      by angel'o'sphere (80593) on Friday March 13, 2009 @01:04PM (#27183657) Homepage Journal


      In THIS house, we obey the laws of thermodynamics.

      Like other posters pointed out: you likely don't know what thermodynamics even is. Hint: thermo has something to do with temperature. Thermodynamcs is about entropy and heat not about magnetic fields or electric fields.

      To your question:
      In other words -- what's preventing the battery from discharging?
      The battery does not discharge in the same way your hard drive is not losing its content just so. The magnetic fields in such a device are static that means they don't move, that means they don't induce anything to anything. However if you read the article (yes the linked article, you can read it, you know!!) you find that nanoscale areas are magnetized and that tunnel effects are involved. I guess that such small areas can "discharge" randomly vie tunnel effects (similar to radioactive decay).

      angel'o'sphere

    • by Khashishi (775369)

      what's preventing the battery from discharging?

      Same thing that keeps any battery from discharging. Time.

  • CAUTION (Score:5, Funny)

    by Waffle Iron (339739) on Friday March 13, 2009 @10:35AM (#27181315)

    Do not open or crush battery. Severe risk of releasing a life-sucking vortex.

    Do not dispose in fire. Doing so could loose a storm of flaming vortices.

    Do not use this battery on carnival rides, while figure skating, or place in spinning clothes washer. Risk of severe gyroscopic reactions, which may lead to property damage, personal injury or death.

    • Re:CAUTION (Score:5, Funny)

      by dazedNconfuzed (154242) on Friday March 13, 2009 @10:47AM (#27181523)

      Do not taunt Magnetic Spin Battery.

    • Re: (Score:2, Funny)

      Warning:

      Do not open or crush battery. Severe risk of releasing a life-sucking vortex.

      Do not post on Slashdot after watching vampire movies. Severe risk of relating every story to sucking life force out of humans.

      Do not dispose in fire. Doing so could loose a storm of flaming vortices.

      Do not post on Slashdot after playing too many video games. Severe risk of hallucinating amazing 3d effects.

      Do not use this battery on carnival rides, while figure skating, or place in spinning clothes washer. Risk of severe gyroscopic reactions, which may lead to property damage, personal injury or death.

      Do not post on Slashdot after dropping acid. May cause visualizations of carnival rides, Bryan Boitano and other spinning objects.

    • Re:CAUTION (Score:4, Funny)

      by Gerafix (1028986) on Friday March 13, 2009 @10:55AM (#27181633)
      You forgot:

      Do not look into spinning battery with remaining eye.

  • Battery Aging (Score:3, Insightful)

    by ChromaticDragon (1034458) on Friday March 13, 2009 @10:35AM (#27181335)

    If this does prove to be useful for batteries, would it eliminate issues related to battery memory?

    It appears current rechargeable batteries "age" due to chemical reactions even if not used. Even more so due to repeated charge cycles.

    With no chemical reactions in play, does this mean people won't be forced to upgrade their phones simply because their battery is all but dead?

    • Re: (Score:2, Insightful)

      With no chemical reactions in play, does this mean people won't be forced to upgrade their phones simply because their battery is all but dead?

      No. There are still five year old children about, and they like taking the batteries out of things, then losing them in the toilet, the cat, the microwave... Trust me, the lack of chemical reactions doesn't diminish the need for replacement parts. -_-

      • "diminish" !== "remove"

        One can imagine something getting smaller without going completely away.

    • Battery memory is dependent on the battery type. Nicad batteries tend to have really terrible memory, and the best way to deal with this is cycling the battery (completely discharging it and recharging it several times.) Or completely discharing/recharging it every time you use it.

      Nickle Metal Hydride batteries, on the other hand, have no memory at all.

      (Used to do a lot of electric RC vehicles)

      • I don't remember, off the top of my head, the deal with NiMH but I do know that while Lithium Ion batteries don't have a traditional "memory", they do degrade over time even if not used. This can be slowed by storing them in a freezer, but it is a problem that most other battery types don't have.

        • by Tony Hoyle (11698) *

          NiMH have a maximum number of full charge/discharge cycles before they start to degrade quite badly. Ask anyone with an older ipod :p

    • by Shrike82 (1471633)

      With no chemical reactions in play, does this mean people won't be forced to upgrade their phones simply because their battery is all but dead?

      This may come as something of a shock, but you can buy a new battery for your existing phone.

      • I'm assuming that the OP was refering to the fact that, sometimes, the cost of buying a new battery is almost as much as just getting a new phone. At that point, there is no reason not to get a new phone as the phones themselves do wear out eventually.

  • I though someone had got the induced decay of Hf spin isomers to work.

    http://en.wikipedia.org/wiki/Induced_gamma_emission [wikipedia.org]

    1300 megajoules per gram would be a good battery.

  • Yeah, but.. (Score:5, Funny)

    by AndrewNeo (979708) on Friday March 13, 2009 @10:42AM (#27181441) Homepage

    Although the actual device... cannot even light up an LED...

    So you're telling me this thing is less powerful than a potato?

    • Yes, but the important question is how big it is. If they created, only, a single "cell" of this tech as a proof of concept then, of course, it would be less powerful than a potato but it would also be too small to see with the naked eye. The idea would be, assuming it weren't possible to improve the efficiency of a single cell, to find a way to scale up to a huge array of these things. If they make a battery the same size as a pototoe, and it's still less powerfull, then you would have a legitimate comp

  • if you spin up a mechanical flywheel, you can later pull back out the energy.
    there are datacenter UPS that run on this principle.
    http://www.google.com/search?hl=en&q=flywheel+ups&start=0&sa=N [google.com]

    the thing is, if they get off balance, the uncontrolled release of the kinetic energy
    (ooh, a car analogy) is similar to a gas tank explosion in destructive capability

    What happens when the spin stored energy releases in an uncontrolled fashion?
    what is the failure analysis of a commercial grade 'spin battery'

    • You're thinking of a single rotating mass, such as a big hunk of metal cut into a flywheel. They're using lots of tiny, independent masses.

      Force = mass * acceleration

      Yo momma's so fat, even duracell doesn't wanna see her spin.
    • "More spin" is really "more aligned spin". In normal matter spin is disordered and aligned randomly in either of two states.
    • by geekoid (135745)

      I would rather imagine someone actually understanding what the article talks about before posting on slashdot.

      Closes eyes *mumblemumblemumble

  • by macraig (621737) <.mark.a.craig. .at. .gmail.com.> on Friday March 13, 2009 @10:51AM (#27181577)

    ... and not all of it from the magnets themselves.

  • by Scareduck (177470) on Friday March 13, 2009 @10:59AM (#27181681) Homepage Journal
    Here's the pre-publication link in Nature [nature.com].

    The electromotive force (e.m.f.) predicted by Faraday's law reflects the forces acting on the charge, â"e, of an electron moving through a device or circuit, and is proportional to the time derivative of the magnetic field. This conventional e.m.f. is usually absent for stationary circuits and static magnetic fields. There are also forces that act on the spin of an electron; it has been recently predicted that, for circuits that are in part composed of ferromagnetic materials, there arises an e.m.f. of spin origin even for a static magnetic field. This e.m.f. can be attributed to a time-varying magnetization of the host material, such as the motion of magnetic domains in a static magnetic field, and reflects the conversion of magnetic to electrical energy. Here we show that such an e.m.f. can indeed be induced by a static magnetic field in magnetic tunnel junctions containing zinc-blende-structured MnAs quantum nanomagnets. The observed e.m.f. operates on a timescale of approximately 10^2-10^3 seconds and results from the conversion of the magnetic energy of the superparamagnetic MnAs nanomagnets into electrical energy when these magnets undergo magnetic quantum tunnelling. As a consequence, a huge magnetoresistance of up to 100,000 per cent is observed for certain bias voltages. Our results strongly support the contention that, in magnetic nanostructures, Faraday's law of induction must be generalized to account for forces of purely spin origin. The huge magnetoresistance and e.m.f. may find potential applications in high sensitivity magnetic sensors, as well as in new active devices such as 'spin batteries'.

    Readers with subscriptions can see the whole paper.

    • Readers with subscriptions can also leak the whole paper.

      • by Anonymous Coward on Friday March 13, 2009 @02:19PM (#27184771)

        Ask and you shall receive...

        Electromotive force and huge magnetoresistance in magnetic tunnel junctions
        Pham Nam Hai1, Shinobu Ohya1,2, Masaaki Tanaka1,2, Stewart E. Barnes3,4 & Sadamichi Maekawa5,6

        Department of Electrical Engineering and Information Systems, The University of Tokyo, 7-3-1 Hongo, Bunkyo-ku, Tokyo 113-8656, Japan
        Japan Science and Technology Agency, 4-1-8 Honcho, Kawaguchi-shi 332-0012, Japan
        Physics Department, University of Miami, Coral Gables, Florida 33124, USA
        TCM, Cavendish Laboratory, University of Cambridge, Cambridge CB3 0HE, UK
        Institute for Materials Research, Tohoku University, Sendai 980-8577, Japan
        CREST, Japan Science and Technology Agency, Tokyo 100-0075, Japan
        Correspondence to: Masaaki Tanaka1,2 Correspondence and requests for materials should be addressed to M.T. (Email: masaaki@ee.t.u-tokyo.ac.jp).

        The electromotive force (e.m.f.) predicted by Faraday's law reflects the forces acting on the charge, -e, of an electron moving through a device or circuit, and is proportional to the time derivative of the magnetic field. This conventional e.m.f. is usually absent for stationary circuits and static magnetic fields. There are also forces that act on the spin of an electron; it has been recently predicted1, 2 that, for circuits that are in part composed of ferromagnetic materials, there arises an e.m.f. of spin origin even for a static magnetic field. This e.m.f. can be attributed to a time-varying magnetization of the host material, such as the motion of magnetic domains in a static magnetic field, and reflects the conversion of magnetic to electrical energy. Here we show that such an e.m.f. can indeed be induced by a static magnetic field in magnetic tunnel junctions containing zinc-blende-structured MnAs quantum nanomagnets. The observed e.m.f. operates on a timescale of approximately 102-103 seconds and results from the conversion of the magnetic energy of the superparamagnetic MnAs nanomagnets into electrical energy when these magnets undergo magnetic quantum tunnelling. As a consequence, a huge magnetoresistance of up to 100,000 per cent is observed for certain bias voltages. Our results strongly support the contention that, in magnetic nanostructures, Faraday's law of induction must be generalized to account for forces of purely spin origin. The huge magnetoresistance and e.m.f. may find potential applications in high sensitivity magnetic sensors, as well as in new active devices such as 'spin batteries'.

        Three ingredients are important to the observation of a large spin-derived e.m.f. The first is an ensemble of superparamagnetic nanometre-sized magnets with a large spin S 200. Owing to a very large magnetic anisotropy, the magnetic moment is aligned along the z direction with a component Sz = S of the spin in this direction. A static magnetic field H = Hz splits these two ground states (with Sz = S) by an energy 2H = 2SgBH (where g is the g-factor and B is the Bohr magneton). It is this appreciable energy difference that drives the e.m.f. Second, these nanomagnets constitute an essential conductive path through our magnetic tunnel junctions (MTJs), but have such a small capacitance C that the Coulomb energy U = e2/(2C) for adding or removing electrons exceeds the thermal energy kBT, effectively blocking sequential electrical conduction3. However, as is commonplace, there are spin-flip channels of many-body origin that conduct under this 'Coulomb blockade'. Third, for a temperature T = 3 K, an S 200 nanomagnet would not usually relax within our ten-minute timescale. However, the spin-flip channels mix Sz = -S with -S+1 and ultimately the two ground states Sz = S. With the conduction of a single electron, relaxation -S S occurs, the electron gains an energy 2SgBH, and for an ensemble this results in a steady current driven by an e.m.f. = 2SgBH/e.

        Normally an MTJ consists of metallic thin-film ferromagnetic electrodes and a thin tunnel barrier made of an insulator. The MTJs in this study are unique (Fig. 1a); they co

  • by MoellerPlesset2 (1419023) on Friday March 13, 2009 @11:11AM (#27181921)
    That we're talking about _spin_ here, as in a property of subatomic particles corresponding to an 'intrinsic' angular momentum, not as in something that's physically 'spinning'. Electrons spin +1/2 or -1/2 and that's it. They can't stop. The energy here is being stored in the form of the _orientations_ of these spins, not the spin itself. What's keeping them that way is conservation of spin. Which is analogous to conservation of angular momentum. (Bound) Electrons can't change their spin state spontaneously. Which is why stuff which is magnetized stays that way for a long time. It's also the reason for phosphorescence. While I think what they've done here is undeniably pretty cool, in turning spin-state transitions into electricity directly, it's probably not going to create any real competition for conventional batteries, for fairly simple reasons. Batteries store electricity in the form of chemical redox states, which means adding/removing electrons from atoms/ions. The energy differences between spin states are typically an order of magnitude smaller than the energy difference between redox states.
    • by Culture20 (968837)
      This type of misunderstanding was bound to happen at some point. Physicists should have chosen their descriptive words for particles better. At least the quark descriptors are weird enough not to be confused with other physics.
  • Theres a limit on how much a material can be magnetized before its self-repellent magnetic energy rips it apart.
  • by Wilson_6500 (896824) on Friday March 13, 2009 @11:42AM (#27182375)
    Spintronics is a little too far out of my ken (I was always more of a radiation physicist, where everything comes in nice little packages instead of fields), but if I'm reading the paper correctly, they're saying that they can apply a static magnetic field to one of these devices and then can measure a voltage drop across a resistor hooked up to the device. They can get a few millivolts from a 1.2 Tesla field, which persists for at least ten minutes but does decay in that time frame. When they remove the magnetic field, the voltage disappears.

    I guess my question is that if the field is static, where is the energy coming from that drives the current giving rise to the voltage? I'm also wondering how one regenerates the voltage after it discharges completely.
    • If I understand the enthusiasm properly, the material could be kept within a static magnetic field (such as found in your average, garden variety medical MRI unit), and energy could be stored and retrieved by directly applying voltages... like a capacitor, except the storage occurs in magnetic spins instead of electric fields. Then removing the charging voltage, the spin energy is slowly released in the form of electrical energy, again similar to a capacitor, but slower.

      They're also doing this really re
  • A battery on the scale of a hair may be fine for driving a car the size of a grain of salt. SInce one always has to take these announcements with a bag of salt, it may work out fine.
  • Link to actual paper (Score:5, Informative)

    by Animats (122034) on Friday March 13, 2009 @12:16PM (#27182929) Homepage

    Bypassing the layers of blogs, here's the actual paper. [nature.com] But it costs $32 to read more than the abstract.

    This is an application of superparamagnetism. [wikipedia.org] Paramagnetism is ordinarily a weak phenomenon, but there are some new materials for which this effect is much stronger.

    It's too early to tell if this is useful. Right now, it's in the category of "minor development in materials science overpromoted as a major breakthrough". It might turn out to have some relevance to MRI imaging or disk drives, both of which rely on fine-scale magnetic effects.

  • How refreshing! It's been quite a while since the last big claim where some tiny physical effect from someone's doctoral thesis or obscure scientific research was overblown far beyond physical reality, and projected to solve great social and economic problems, produce enormous wealth for its inventors, bring justice to the world, cure herpes, feed the hungry, blah blah blah.
  • I don't know if anyone else has noticed yet, but buzzspeak is on average, substantially down in the last few months. The recession has begun to bite and the surfing the financial high tide with radical new buzzwords is no longer a winning strategy. This is the first piece of buzz speak I've heard in quite a while to be honest.

    The game has changed, and the language along with it.

  • ... a flying car, or they're just wasting our time!

The meta-Turing test counts a thing as intelligent if it seeks to devise and apply Turing tests to objects of its own creation. -- Lew Mammel, Jr.

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