a few years ago, carbon nanofoam is the fifth known
allotrope of carbon,the others being graphite, diamond,
fullerene (e.g., C-60 molecules), and carbon nanotubes.
The foam is, along with aerogel,one of the lightest
known solid substances (with a density of ~2 mg/cm^3).
But at this week's APS March Meeting in Montreal, physicists
announced an even more interesting property: though
entirely from carbon atoms that are normally considered
nonmagnetic, the foam nevertheless can act like a ferromagnet.
a high-power laser at disordered solid carbon, a Greece-Australia-Russia
research collaboration (John Giapintzakis, University
of Crete/IESL-FORTH, firstname.lastname@example.org and Andrei
Rode, Australian National University, email@example.com)creates
a gossamer web made of carbon-atom clusters (with
an average diameter of 6-9 nanometers) randomly interconnected.
The foam has other interesting properties: it also
is a semiconductor, making it
attractive for device applications.
most salient property of carbon nanofoam, however,
is its magnetism. Unlike other forms of carbon, such
as graphite and diamond, freshly produced carbon nanofoam
is ferromagnetic; that is, it is initially attracted
strongly to a permanent magnet at room temperature.
Although the room-temperature ferromagnetic behavior
disappears after a few hours, it persists at lower
Consequently this "ferromagnetic semiconductor"
might have very useful applications for spintronics,
the emerging field of devices based on a material's
the initial skepticism about pure carbon having ferromagnetic
properties, the researchers acknowledged that they
found traces of iron and nickel impurities in their
foam, but calculated that the small amounts of these
magnetic materials could only account for 20% of the
strength of the ferromagnetic fields in the foam.
Researchers have concluded that the observed novel
magnetic behavior is an intrinsic property of the
carbon nanofoam and can be traced to its complex
microstructure. Namely, carbon atoms in the foam forms
heptagon structures, 7-corner, 7-edge polygons that
have an unpaired electron, one that does not form
a chemical bond and has a magnetic moment which may
lead to the magnetism.
researchers also have preliminary indications that
the novel magnetic behavior also occurs in another
nano-compound made of boron and nitrogen, two other
elements that are ordinarily non-magnetic.
at an APS news conference, theoretical collaborator
David Tomanek of Michigan State (firstname.lastname@example.org)
said that he hoped that the carbon nanofoam and similar
compounds would remove what he termed a "magnetic
prejudice," the idea than an element should be
stereotyped as either magnetic or nonmagnetic. One
possible application of the carbon nanofoam is in
biomedicine, as tiny ferromagnetic clusters that could
be injected in blood vessels may significantly increase
the quality of magnetic resonance imaging pictures.