Scientists from IBM's Almaden Research
Center have measured the energy required to flip the magnetic orientation,
or spin of a single atom trapped on a surface.
As magnetic data storage devices become smaller it is becoming
more important to understand the interactions between single magnetic
atoms and their surrounding environments. This ability is also important
in the development of spintronics devices, which are made up of low-power
circuits that use the spin of electrons rather than their charge to represent
the 1s and 0s of computer information, and quantum computing, which employs
quantum properties like spin to carry out computations.
The researchers found that the minimum energy required to flip
a manganese atom oriented in a 1.4-tesla magnetic field is about five
ten-thousandths of an electron volt. An ordinary kitchen magnet has a
strength of about one-tenth of a tesla. A single photon of visible light
has about two electron volts of energy, which is about 4,000 times the
energy required to flip the atom.
The researchers used a modified scanning tunneling microscope
to apply and measure the energy needed to flip manganese atoms placed
on patches of aluminum oxide on a nickel-aluminum surface in a vacuum
at near-absolute zero.
The researchers also found that it takes 6.5 percent more energy
to flip an atom at the edge of an aluminum oxide patch then it does to
flip one near the center of patch.
It will be 10 to 20 years before spin-based devices are ready
for practical application, according to the researchers. The work appeared
in the September 9, 2004 issue of Science.
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