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A NEWLY discovered class of magnetic materials could help to make electrical
transformers ultra-efficient, cutting the energy losses in devices ranging from
CD players to electricity sub-stations.

The new material is a 鈥渘anocomposite鈥�. It is made up of submicroscopic
particles just 8 nanometres in diameter embedded in a solid matrix. Normally,
the particles are locked into the material and are unable to move. But Ron Ziolo
and his colleagues at the Xerox Laboratory for Magnetics Research at the
University of Barcelona have discovered a way of 鈥渦nbonding鈥� the particles so
that they can rotate freely in voids within the material.

The team began by adding nanoparticles of iron oxide to a methanol-based
liquid polymer and then cooling the mixture to 4.2 kelvin, the temperature of
liquid helium. This created a frozen methanol polymer matrix in which the
nanoparticles were held within minute cavities. 鈥淚 think of the structure as a
bit like a sponge in which the particles are able to carve out some space for
themselves,鈥� says Ziolo.

The particles were initially immobile, bonded firmly to the insides of their
cavities. But Ziolo鈥檚 team discovered that applying a small alternating magnetic
field sets the particles free. He believes that this happens because the surface
of the cavities somehow repels the nanoparticles, allowing them to rotate.

Because the nanoparticles rotate like tiny compasses and align themselves
with any applied field, there is almost no energy loss when the field is
changed. 鈥淣o other material demonstrates this property,鈥� says Ziolo.

The breakthrough could lead to a new generation of electrical transformers.
Transformers usually contain iron cores, which heat up as the magnetic field
induced by alternating current passing through coils wound round them switches
back and forth. The energy lost as heat is a major curb on their performance.
Replacing the iron core with a nanocomposite could reduce energy loss, allowing
transformers to become both smaller and more efficient.

Sara Majetich, a physicist at Carnegie Mellon University in Pittsburgh, says
the work is very interesting from a scientific point of view. 鈥淚鈥檇 like to see
more work characterising the properties of this material,鈥� she adds. The team
speculates that the new material could also act as a 鈥�3D compass鈥�, as the
nanoparticles align themselves with the Earth鈥檚 magnetic field.

Ziolo is working on a version of the material that he says works at room
temperature. And he says that newer versions that contain non-magnetic
nanoparticles might have interesting acoustic, thermal or optical properties.