Eiji Saitoh of Keio
University in Yokohama, Japan,
and his collaborators found that heating one side of a magnetized nickel-iron rod
changes the arrangement of the electrons in the material according to their
spins. These spins are the quantum-physics analogs of the south-north magnetic
axes in bar magnets.
In the heated rod, electrons with spins that are aligned “up,”
or with the material’s magnetic field, tend to prefer the warmer side, while those
with spins pointing in the opposite direction, or “down,” tend to prefer the
cooler side, the researchers report in the Oct. 9 Nature.
Engineers could harness this spin effect to design new
devices for computer chips, Saitoh says. For example, a spintronic battery
could produce spin imbalances at its two electrodes, and the chip could use
that imbalance, instead of an ordinary electric current, and store information
magnetically. Electric currents produce heat, but transferring information by
flipping spins does not. Such spintronics devices would then cut down power
consumption and operate at faster speeds without overheating.
The team calls the newly discovered phenomenon the spin
Seebeck effect, in analogy with the thermoelectric effect discovered by physicist
Thomas Johann Seebeck in the 1800s. In the thermoelectric effect, heating one
side of an electrically conducting rod creates a voltage, because electrons at
the warmer end become faster as they heat up and thus tend to move toward the
cooler end, just like a heated gas tends to expand.
Read more here (ScienceNews)
