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Topic Name: A way to switch a material’s magnetic properties from ‘hard’ to ‘soft’ and back again
Category: Nanocharacterization
Research persons: Professor Gabriel Aeppli,
Location: London Centre for Nanotechnology,17-19 Gordon Street,WC1H 0AH, United Kingdom
Details
An international research team, led by scientists at the London Centre for
Nanotechnology (LCN) and the University of Chicago, has found a way to switch a
material’s magnetic properties from ‘hard’ to ‘soft’ and back again – something
which could pave the way to new control of electromagnetic devices. The research
will appear in the journal Nature on August 2nd and it shows how a magnet can be
‘tuned’ by subjecting it to a second magnetic field, perpendicular to the
original.
Magnets can be classified by their ‘hard’ or ‘soft’ magnetic properties. Hard
magnets, sometimes called ‘permanent’ magnets, have fixed or ‘pinned’ domain
walls which mean the material stays magnetized for a long time. Soft magnets
have moveable domain walls that can be easily flipped. These materials exhibit
impermanent magnetic properties.
Professor Gabriel Aeppli, Director of the LCN and a senior member of the
research team, explained the significance of the research: “Whether a magnet is
hard or soft determines what you can use it for. Typically, you would use a
permanent magnet to fix a note to the door of your refrigerator because you want
it to stay there for a long time. On the other hand, you might use a soft magnet
in a motor or transformer because it would be better at adapting to the rapid
changes in alternating current and would dissipate much less energy than a hard
magnet.
“It is very rare to be able to continuously tune wall pinning in a magnet but we
have now shown how it can be done in a model magnet at a low temperature. In the
process, we demonstrate a new route to applications of magnets at higher
temperatures and show how chemical disorder at the nanometer (one billionth of a
meter) scale can have a huge effect on the properties of a macroscopic
(centimeter scale) magnet .”
Most physical and biological systems can be thought of as disordered.
Semiconductors rely on randomly placed impurities for their electrical
properties and uses, while the chemical and structural impurities in magnets
determine the domain wall pinning and therefore how easily their polarity can be
changed.
“From a theoretical point of view, it’s been really interesting for us to see
the properties of a large, disordered system being dominated to such an extent
by a rare configuration of impurities,” says Professor Aeppli. “Unlike
biological systems, in materials science we are used to seeing behavior which is
dominated by the average characteristics of the system. Here we can observe the
massive influence of a miniscule number of chemical and structural defects.”
About Researcher:
Professor Gabriel Aeppli,
Contact details:
Office: 5P1
Tel: +44 (0)20 7679 0055
Ext: 30055
Fax: +44 (0)20 7679 0595
Email: lcn-administrator@ucl.ac.uk
Funded:
Work at the London Centre for
Nanotechnology was funded by the UK
Engineering and Physical Sciences Research Council and
a Wolfson-Royal Society
Research Merit Award. Research carried out at the
University of Chicago was supported by the
US Department of Energy and
National Science Foundation.
Images:
1. A hi-res image of domain wall patterns in a ferromagnet can be obtained
from Dave Weston at the London Centre for Nanotechnology (see contact details
above)
2.Professor Gabriel Aeppli
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