Scientists
at the University of Massachusetts Amherst report that for the first time they
have designed a much simpler method of preparing ordered magnetic materials
than ever before, by coupling magnetic properties to nanostructure formation at
low temperatures.
The
innovative process allows them to create room-temperature ferromagnetic
materials that are stable for long periods more effectively and with fewer
steps than more complicated existing methods. The approach is outlined by UMass
Amherst polymer scientist Gregory Tew and colleagues in Nature
Communications.
Tew
explains that his group’s signature improvement is a one-step method to
generate ordered magnetic materials based on cobalt nanostructures by encoding
a block copolymer with the appropriate chemical information to self-organize
into nanoscopic domains. Block copolymers are made up of two or more
single-polymer subunits linked by covalent chemical bonds.
The
new process delivers magnetic properties to materials upon heating the sample
once to a relatively low temperature, about 200 C, which transforms them into
room-temperature, fully magnetic materials. Most previous processes required
either much higher temperatures or more process steps to achieve the same
result, which increases costs, Tew says.
He
adds, “The small cobalt particles should not be magnetic at room
temperature because they are too small. However, the block copolymer’s
nanostructure confines them locally which apparently induces stronger magnetic
interactions among the particles, yielding room-temperature ferromagnetic
materials that have many practical applications.”
“Until
now, it has not been possible to produce ordered, magnetic materials via block
copolymers in a simple process,” Tew says. “Current methods require
multiple steps just to generate the ordered magnetic materials. They also have
limited effectiveness because they may not retain the fidelity of the ordered
block copolymer, they can’t confine the magnetic materials to one domain of the
block copolymer, or they just don’t produce strongly magnetic materials. Our
process answers all these limitations.”
Magnetic
materials are used in everything from memory storage devices in our phones and
computers to the data strips on debit and credit cards. Tew and colleagues have
discovered a way to build block copolymers with the necessary chemical
information to self-organize into nanoscopic structures one millionth of a
millimeter thin, or about 50,000 times thinner than the average human hair.
Earlier
studies have demonstrated that block copolymers can be organized over
relatively large areas. What makes the UMass Amherst research group’s results
so intriguing, Tew says, is the possible coupling of long-range organization
with improved magnetic properties. This could translate into lower-cost
development of new memory media, giant magneto-resistive devices and futuristic
spintronic devices that might include “instant on” computers or computers
that require much less power, he points out.
He
adds, “Although work remains to be done before new data storage
applications are enabled, for example making the magnets harder, our process is
highly tunable and therefore amendable to incorporating different types of
metal precursors. This result should be interesting to every scientist in
nanotechnology because it shows conclusively that nano-confinement leds to
completely new properties, in this case room temperature magnetic
materials.”
“Our
work highlights the importance of learning how to control a material’s
nanostructure. We show that the nanostructure is directly related to an
important and practical outcome, that is, the ability to generate
room-temperature magnets.”
“Our
work highlights the importance of learning how to control a material’s
nanostructure. We show that the nanostructure is directly related to an
important and practical outcome, that is, the ability to generate room
temperature magnets.” As part of this study, the UMass Amherst team also
demonstrated that using a block copolymer or nanoscopic material results in a
material that is magnetic at room temperature. By contrast, using a
homopolymer, or unstructured material, leads only to far less useful non- or
partial-magnetic materials.
