View Full Version : Magnetic Spin Batteries
03-17-2009, 09:29 PM
Has anyone ever heard of this type of battery before?
At first, I thought the post was referring to mechanical batteries, like in F1's KERS system. (you know, they spin really fast) These magnetic "spin" batteries are just the opposite, supposedly - no moving parts!
Interesting. The kind of "spin" they are referring to is the first thing I think of when I hear the word. This is actually related to my field (sometimes called spintronics). I'll have to get around to reading the Nature article at some point.
Wouldn't expect an actual product any time soon, though. Likely some cool physics, but not clear it's really better than conventional batteries, in spite of the researcher's spin (ah ha!).
The "spin" they are referring to is a wholly quantum mechanical property. It refers to intrinsic (quantized) angular momentum. I guess most people learn something about it in high school chemistry classes in the context of the Pauli exclusion principle of electrons. This spin angular momentum is separate from the orbital angular momentum (s, p, d, etc. electron shells).
The marketing guys will be sure to "spin" that for all it's worth!
Researchers at the University of Miami and at the Universities of Tokyo and Tohoku, Japan, have been able to prove the existence of a “spin battery,” a battery that is “charged” by applying a large magnetic field to nano-magnets in a device called a magnetic tunnel junction (MTJ)…..
The device created by University of Miami Physicist Stewart E. Barnes, of the College of Arts and Sciences and his collaborators can store energy in magnets rather than through chemical reactions. Like a winding up toy car, the spin battery is “wound up” by applying a large magnetic field –no chemistry involved. The device is potentially better than anything found so far, said Barnes.
“We had anticipated the effect, but the device produced a voltage over a hundred times too big and for tens of minutes, rather than for milliseconds as we had expected,” Barnes said. “That this was counterintuitive is what lead to our theoretical understanding of what was really going on.”
The secret behind this technology is the use of nano-magnets to induce an electromotive force. It uses the same principles as those in a conventional battery, except in a more direct fashion. The energy stored in a battery, be it in an iPod or an electric car, is in the form of chemical energy. When something is turned “on” there is a chemical reaction which occurs and produces an electric current. The new technology converts the magnetic energy directly into electrical energy, without a chemical reaction. The electrical current made in this process is called a spin polarized current and finds use in a new technology called “spintronics.”
The new discovery advances our understanding of the way magnets work and its immediate application is to use the MTJs as electronic elements which work in different ways to conventional transistors. Although the actual device has a diameter about that of a human hair and cannot even light up an LED (light-emitting diode–a light source used as electronic component), the energy that might be stored in this way could potentially run a car for miles. The possibilities are endless, Barnes said.
How can you not be intrigued by the use of the word "counterintuitive"?
I prefer actual understanding to "theoretical understanding" when it comes to practical applications.
Science Daily: Spin Battery: Physicist Develops Battery Using New Source Of Energy (http://www.sciencedaily.com/releases/2009/03/090311162807.htm)
Magnetic 'Spin Battery' Announced (http://www.physicsforums.com/showthread.php?t=299308)
IBM Research | Almaden Research Center | IBM-Stanford Spintronic Science and Applications Center Events (http://www.almaden.ibm.com/spinaps/events/)
Physics - Lending an iron hand to spintronics (http://physics.aps.org/articles/v2/6)
In this context "theoretical understanding" means actual understanding. You see something unexpected, perhaps even counterintuitive in the lab, it's important to have a mathematical model that explains what's going on. Hopefully that model is consistent with existing theory (if you're just trying to graduate). If it doesn't then that can be very interesting scientifically and at the same time very frustrating. Perhaps you have some new physics, but that's hard to prove. More likely than not, you've just missed something. You need a proper theoretical understanding before you really know what's going on.
However, engineers can often make something useful out of certain effect without actual understanding.
Btw, at some point or another, I've had collaborators at all three of those universities (well University of Florida, not necessarily Miami). They're all known for having good high magnetic field laboratories.
I've actually have spent a good amount of time in the Tokyo lab (part of the reason I learned Japanese). They can be some pretty dramatic experiments. The type of thing where you make a building wide danger announcement over the PA. Press a big red button in a room separate from the experiment. The actual experiment sits in a steel reinforced chamber. That red button closes a huge bank of air gap capacitors, that sit in yet another chamber, sending 5 megaJoules of electricity in only a millisecond through a coil producing a magnetic field of up to 650 Tesla (!!!) before exploding with a very big noise. ...and you pray that all your instruments recorded the data.
Access : Electromotive force and huge magnetoresistance in magnetic tunnel junctions : Nature (http://www.nature.com/nature/journal/vaop/ncurrent/full/nature07879.html)
Doug, are you thinking of going to that IBM event?
Slashdot | "Spin Battery" Effect Discovered (http://hardware.slashdot.org/article.pl?sid=09/03/13/1354232)
A new spin on battery technology | Cutting Edge - CNET News (http://news.cnet.com/8301-11386_3-10194885-76.html)
...you have to apply a huge magnetic field to a magnetic material to eek a few spin polarized electrons out of it within seconds.
this could never be useful as a "battery" as we know it.
totally misleading headline.
a capacitor is a better charge storing device...