Magnetics Business & Technology - Spring 2015 - (Page 4)
Noncommittal Material Could Make for Hypersensitive Magnetic
While the mysterious, unseen forces magnets project are now (mostly) well-understood,
they can still occasionally surprise us. For instance, thin films of cobalt have been observed to
spontaneously switch their poles, something that typically doesn't happen in the absence of an
external magnetic field. Physicists at
the National Institute of Standards
and Technology (NIST) and the University of Maryland (UMD) have
measured this phenomenon on the
largest scale yet.
Most magnets are "permanent,"
meaning a magnetic field of some
strength must be applied to reverse
their north and south poles. This
permanence enables the billions of
tiny magnets in hard drives to re(Left) Polarization sensitive light microscopy shows the
liably store data. And smartphone
pattern of north poles (black) and south poles (white)
compasses use nanomagnetic sen- on thin layer of magnetic cobalt. (Right) The researchers
sor technology to detect the Earth's found that the pattern of north poles and south poles
spontaneously fluctuates over time. Strongly fluctuating
At the present time, creating and areas are encoded here as brighter colors. Researchers
detecting these magnetic fields hope to use this data to make more sensitive magnetic
takes a good deal of energy. Making materials whose domains can be flipped more energy efthese devices more energy efficient ficiently, a boon to those with rapidly dying smartphone
batteries. Images show an area approx. 75 micrometers
will require more sensitive magnets
across. Credit: Balk/NIST
that can be influenced by small
magnetic or electric fields. However,
as these magnets become more sensitive, they also become more unstable, flipping from north
to south and back, even with no magnetic field.
The NIST/UMD team mapped out this instability in a film of cobalt, only a few atoms thick,
and determined the conditions under which the instability arises. They hypothesize that the
development of magnetic technology will benefit from their continuously flipping cobalt films,
which can function as extremely sensitive magnetic test beds. Many proposed devices implement layers of ferromagnetic material that must be individually controlled by electric fields to
According to NIST researcher Andy Balk, however, most magnetic materials are too stable to
be influenced at all by electric fields, and researchers have no way of knowing if their proposed
devices are even close to working.
"As an alternative," Balk said, "we could make a proposed magnetic device from our unstable
film. This way, even if the film were influenced only a very small amount, we would see, for example, slightly more north flips than south flips, and we would know we are on the right track."
The current measurements were done with video-rate Kerr microscopy, a form of polarized
light microscopy that can image the fine-grained details of a material's magnetic state. The
scientists found that if undisturbed by outside influence, the magnetic fluctuations in the thin
cobalt film interact with each other; a fluctuation from north to south will always have a corresponding nearby fluctuation from South to North.
Interestingly, these fluctuations exhibit scale invariance, meaning that their behavior is the
same regardless of the length scale on which they are observed, a property they share with
otherwise unrelated phenomena such as earthquakes and crumpling paper.
The researchers are continuing this work at NIST by developing these thin films into sensitive
field detectors for computing and biomedical applications.
Hybrid Multiferroics for Data Storage and New Wireless Applications
To exploit and control magnetism, technology often relies on electromagnets, which limit
hardware configurations due to their size and energy consumption. As an alternative, scientists
are beginning to develop hybrid nanomaterials that are responsive to both electric and magnetic fields. These materials can save energy and space, and are opening doors to a wealth of
new technological applications
Creating materials that can be influenced by both magnetic and electric forces, so called
'multiferroics', is an emerging field that is currently being addressed mainly by academics, al-
Magnetics Business & Technology * Spring 2015
Volume 14, Issue 1
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Table of Contents for the Digital Edition of Magnetics Business & Technology - Spring 2015
First-Order-Reversal-Curve Analysis of Multi-Phase Ferrite Magnets
Magnetics Design Tool for Power Applications
Magnet Inspection Tool with High Magnetic and Mechanic Accuracy
Research & Development
Software & Design
Marketplace / Advertising Index
Spontaneous Thoughts: The Patent Challenge
Magnetics Business & Technology - Spring 2015