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Topic Name: New Iron based and High Temperature Superconductor
Category: Advanced packaging and interconnection technologies
Research persons: C. de la Cruz, Q. Huang, J.W. Lynn, J. Li, W. Ratcliff II, J.L. Zarestky
Location: NIST, Gaithersburg, MD, United States
Details
GAITHERSBURG, MD—In the initial studies of a new class of high-temperature
superconductors discovered earlier this year, research at the Commerce
Department’s National Institute of Standards and Technology (NIST) has revealed
that new iron-based superconductors share similar unusual magnetic properties
with previously known superconducting copper-oxide materials. The research
appears in the May 28 Advanced Online Publication of the journal Nature.
These superconductors may one day enable energy and environmental gains
because they could significantly heighten the efficiency of transferring
electricity over the electric grid or storing electricity in off-peak hours for
later use.
“While we still do not understand how magnetism and superconductivity are
related in copper-oxide superconductors,” explains NIST Fellow Jeffrey Lynn at
the NIST Center for Neutron Research (NCNR), “our measurements show that the new
iron-based materials share what seems to be a critical interplay between
magnetism and superconductivity.”
The importance of magnetism to high-temperature superconductors is remarkable
because magnetism strongly interferes with conventional low-temperature
superconductors. “Only a few magnetic impurities in the low-temperature
superconductors sap the superconducting properties away,” says Lynn.
By contrast, copper-oxide superconductors, discovered in 1986, tolerate
higher magnetic fields at higher temperatures. The highest performance
copper-oxide superconductors conduct electricity without resistance when cooled
to "transition temperatures" below 140 Kelvin (-133 Celsius) and can simply and
cheaply be cooled by liquid nitrogen to 77 Kelvin or (-196 Celsius).
Japanese researchers discovered earlier this year that a new class of
iron-based superconducting materials also had much higher transition
temperatures than the conventional low-temperature superconductors. The
discovery sent physicists and materials scientists into a renewed frenzy of
activity reminiscent of the excitement brought on by the discovery of the first
high-temperature superconductors over 20 years ago.
Earlier work on the copper-oxide superconductors revealed that they consist
of magnetically active copper-oxygen layers, separated by layers of non-magnetic
materials. By “doping,” or adding different elements to the non-magnetic layers
of this normally insulating material, researchers can manipulate the magnetism
to achieve electrical conduction and then superconductivity.
The group of scientists studying the iron-based superconductors used the NCNR,
a facility that uses intense beams of neutral particles called neutrons to probe
the atomic and magnetic structure of the new material.
As neutrons probed the iron-based sample supplied by materials scientists in
Beijing, they revealed a magnetism that is similar to that found in copper-oxide
superconductors, that is, layers of magnetic moments—like many individual bar
magnets—interspersed with layers of nonmagnetic material. Lynn notes that the
layered atomic structure of the iron-based systems, like the copper-oxide
materials, makes it unlikely that these similarities are an accident.
One of the exciting aspects of these new superconductors is that they belong
to a comprehensive class of materials where many chemical substitutions are
possible. This versatility is already opening up new research avenues to
understand the origin of the superconductivity, and should also enable the
superconducting properties to be tailored for commercial technologies.
Researchers from the following institutions partnered with NIST in these
studies: University of Tennessee, Knoxville; Oak Ridge National Laboratory;
University of Maryland; Ames Laboratory; Iowa State University and the Chinese
Academy of Sciences’ Beijing National Laboratory for Condensed Matter Physics.
C. de la Cruz, Q. Huang, J.W. Lynn, J. Li, W. Ratcliff II, J.L. Zarestky,
H.A. Mook, G.F. Chen, J.L. Luo, N.L. Wang and P. Dai. Magnetic order close to
superconductivity in the iron-based layered La(O1-xFx)FeAs systems. Nature
Advanced Online Publication, May 28, 2008.
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