If the news item had appeared anywhere other than EurekAlert I’d have blown it off. Then the press release subtitle of “His discovery is a ‘proof of principle’ of the existence of a ‘spin battery’” both baited and repelled me. Press releases can be devilish things.
Yet the paper and the supplemental notes make a good case that the research has in fact yielded a result that Faraday had predicted way more than a century ago such that the forces acting on the charge of an electron moving through a device or circuit is proportional to the time derivative of the magnetic field. Of late is the prediction that, for circuits that are in part composed of ferromagnetic materials, there arises an electromagnetic field of spin origin even for a static magnetic field. This electromagnetic field 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.
Briefly, moving a magnet past a conductor moves electrons and the theory suggests that new magnetic fields are formed as well, usually seen as magnetic polarity. So far it seems real and quite believable. Now add a huge magnetoresistance of up to 100,000 per cent is observed for certain bias voltages. That’s a mighty large increase, and seems totally counter intuitive. Which is just what the researchers thought.
University of Miami Physicist Stewart E. Barnes, of the College of Arts and Sciences and with his collaborators at the Universities of Tokyo and Tohoku, Japan, have created a device that can store energy in magnets rather than through chemical reactions. Their paper is published by Nature.
Barnes says, “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. That this was counterintuitive is what lead to our theoretical understanding of what was really going on.”
The principal of the new technology is the use of nano-magnets to induce an electromotive force. Like a conventional battery, except in a more direct fashion, the energy is stored in a battery in the form of chemical energy. When something is turned “on” a chemical reaction is triggered, which occurs and produces an electric current. The new technology converts stored magnetic energy directly into electrical energy, without a chemical reaction. The electrical current made in this process is being called a spin polarized current and could be brought to use in a new technology now called “spintronics.”
The new battery is “charged” by applying a large magnetic field to nano-magnets in a device called a magnetic tunnel junction. The research 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 electromagnetic field may find potential applications in high sensitivity magnetic sensors, as well as in new active devices such as ’spin batteries’.
All that is a ‘stretch’ in more skeptical terms, nevertheless, the new discovery advances understanding of the way magnets work and its immediate application is to use the magnetic tunneling junctions as electronic elements which work in different ways than for example conventional transistors. The actual research device has a diameter about that of a human hair and cannot even light up a light-emitting diode – yet the energy that might be stored in this way could potentially run a car for miles. Barnes said the possibilities are endless. I dare agree he may be right.
There is a very, very long way to go. The ability to generate a magnetic field is nothing new nor is fixing one onto a piece of metal. But to set up a multitude of them in a single structure, measure and extract the power saved within and find that the gain reached in the early lab phase to such an incredible expansion is a sure motivator for more research.
The paper will surely trigger others to try to duplicate the results. Should confirmation be forthcoming one can fairly expect progress to come fast and furious. There are several striking products uses that come to mind, memory storage and power storage being the obvious leaders.
At conception and first proof the possibilities are subject to imaginative ideas. Just thinking of all the magnets in modern life causes one to consider – if this technology does become an energy storage medium – the amount that could be harbored under control might be a very large amount indeed.
So a good shot of encouragement is in order. Once confirmed, these folks’ innovations and development are just beginning to be understood, and the possibilities are uncountable.
Interested or intrigued? You’re going to need to check out the paper at Nature.