Researchers and manufactures routinely
dope, or add impurities too, semiconductors like silicon to give the material
specific electrical properties. Researchers are also working out ways
to dope silicon to control its magnetic properties.
Devices made from magnetic semiconductors can make use of the
spin of the electron in addition to its charge. These spintronics devices
are potentially faster and consume less power than today' electronics.
Researchers from the State University of New York at Albany have
found a way to make silicon ferromagnetic at room temperature. Ferromagnetic
materials respond strongly to magnetic fields and remain magnetic after
an external magnetic field has been removed. This opens the door to developing
spintronics devices using the material of computer chips, which is easily
manufactured using existing facilities.
The researchers implanted silicon with manganese ions to make
a material that retains its ferromagnetic properties at temperatures as
high as 127 degrees Celsius. The researchers doped the silicon at two
concentrations of manganese: 0.1 percent and 0.8 percent. They found that
the level of magnetism depends on the concentration of manganese, the
temperature, and whether the silicon has been doped to be a positive or
negative charge carrier.
The researchers' next steps are to more fully understand the electronic
and physical structure of the material in order to determine the origin
of the ferromagnetism.
The device could be ready for practical use in five to ten years,
according to the researchers. The work appeared in the January 4, 2005
issue of Physical Review B.
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