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ScienceDaily (July 11, 2012) — Researchers who are studying a new magnetic effect that converts heat to electricity have discovered how to amplify it a thousand times over -- a first step in making the technology more practical.
In the so-called spin Seebeck effect, the spin of electrons creates a current in magnetic materials, which is detected as a voltage in an adjacent metal. Ohio State University researchers have figured out how to create a similar effect in a non-magnetic semiconductor while producing more electrical power.
They've named the amplified effect the "giant spin-Seebeck" effect, and the university will license patent-pending variations of the technology.
The resulting voltages are admittedly tiny, but in this week's issue of the journal Nature, the researchers report boosting the amount of voltage produced per degree of temperature change inside the semiconductor from a few microvolts to a few millivolts -- a 1,000-fold increase in voltage, producing a 1-million-fold increase in power.
Great progress has been made in understanding how the spin-Seebeck effect works, but many details are still a mystery. Though researchers around the world have been able to reproduce the spin-Seebeck effect with some success since it was discovered at Tohoku University in 2008, a unified theory is lacking. And the same holds true for the giant spin-Seebeck effect, though the Ohio State researchers have several suggestions as to what's going on.
People may be familiar with the concept of light being made of particles called photons, Heremans said. Heat, too, can be thought of the same way, and scientists have a similar-sounding name for heat particles: phonons.
The researchers think that they were able to induce a powerful stream of phonons inside the semiconductor. The phonons then smashed into the electrons and knocked them forward, while the atoms in the semiconductor made the electrons spin as they streamed through the material -- like a bullet spinning in a rifle barrel.
Roberto Myers, assistant professor of materials science and engineering, said that the key to making the experiment work was the choice of materials.
Since the material was non-magnetic, they needed to create a magnetic field around it and lower the temperature to polarize the electrons.
Heremans and his team are exploring other materials -- magnetic and otherwise -- to push the effect further.
I've always toyed with the idea of form of cryogenic container around a highly ionized hydrogen plasma that may be a new form of battery. Although, that barely scratches the surface on how it would work. Pure fantasy maybe...