Discovery of New Iron-Platinum-Based High-Temperature Superconductor (Press Release)
- Release Date
- 15 Sep, 2011
- BL02B1 (Single Crystal Structure Analysis)
- BL02B2 (Powder Diffraction)
Okayama University
A research group led by Minoru Nohara (professor of quantum physics in condensed matter), Kazutaka Kudo (assistant professor of quantum physics in condensed matter), and Satomi Kakiya (graduate student) of the Graduate School of Natural Science and Technology, Okayama University, has discovered a new high-temperature superconductor containing iron and platinum. Its superconductivity transition temperature is 38 K (-235 oC), which is the third highest ever reported for an iron-based superconductor. The results of this research were published as a Paper of Editors' Choice (noteworthy paper)*1 in the September issue of the Journal of the Physical Society of Japan (JPSJ). A research group led by Minoru Nohara (professor of quantum physics in condensed matter), Kazutaka Kudo (assistant professor of quantum physics in condensed matter), and Satomi Kakiya (graduate student) of the Frontier and Fundamental Sciences Division, Graduate School of Natural Science and Technology, Okayama University, has discovered a new iron-platinum-based high-temperature superconductor with the formula Ca10(Pt4As8)(Fe2-xPtxAs2)5, in collaboration with a research group led by Hiroshi Sawa (professor of structural physics engineering) of the Department of Applied Physics, Graduate School of Engineering, Nagoya University. The transition temperature of this compound, at which the material starts to exhibit superconductivity,*2 is 38 K (-235 oC), which is the third highest ever reported for an iron-based superconductor.*3 This new superconductor has an atomic arrangement in which iron arsenide (FeAs) layers responsible for the superconductivity and interlayers called spacer layers are alternately stacked. It has been considered that superconductivity can be achieved at higher temperatures by manipulating the chemical composition and atomic arrangement of such spacer layers, and scientists worldwide have investigated new combinations of elements. The superconductor discovered in this research contains spacer layers with a completely new combination of elements with the formula Ca10(Pt4As8), attracting attention as a material that can contribute to the development of new high-temperature superconductors.*4 The superconductor Ca10(Pt4As8)(Fe2-xPtxAs2)5 has as many as 21 atoms in each repeated unit of the atomic arrangement. The determination of such a complicated atomic arrangement has recently become possible by performing synchrotron radiation X-ray diffraction experiments using the single-crystal structure analysis beamline (BL02B1) and the powder diffraction beamline (BL02B2) at SPring-8. The superconductor, whose atomic arrangement was determined to be triclinic at SPring-8, has the lowest symmetry and the most complicated atomic arrangement among the reported superconductors.*5 Publication: |
<<Glossary>>
*1 Paper of Editors' Choice (noteworthy paper)
Two papers, including the paper on the new superconductor discovered in this research, were selected as "Papers of Editors' Choice (noteworthy papers)" from among a total of 45 papers published in the September issue of JPSJ. Certificates were given to all authors of the awarded papers (Photograph 1).
*2 Superconductivity
In 1911, exactly 100 years ago, the Dutch physicist Kamerlingh Onnes discovered superconductivity, in which electrical resistance (electrical loss) drops to zero below a transition temperature. Currently, superconductivity is practically used in magnetic resonance imaging (MRI) for medical purposes and superconducting magnets for linear motor cars. In the Sharp Kameyama Plant, electric power is stably supplied by superconducting magnetic energy storage (SMES) systems (with momentary voltage drop compensation). To realize zero-loss electric transmission using superconducting wires, it is necessary to develop superconductors with higher transition temperatures. When superconducting electric transmission is realized, it will be possible to save electric power equivalent to the output of six nuclear power plants with an annual capacity of millions of kilowatts. In the Sahara Solar Breeder Project, photovoltaic power generation is planned to take place in the Sahara Desert with the generated power transmitted to various countries via superconducting wires.
*3 Iron-based superconductors
In 2008, Hideo Hosono and colleagues of Tokyo Institute of Technology discovered the first iron-based superconductor. To date, GdFeAsO is the iron-based superconductor with the highest transition temperature of 56 K (-217 oC). This is followed by Ca4(Mg,Ti)3O8Fe2As2, in which superconductivity at 47 K (-226 oC) was discovered by Jun-ichi Shimoyama and colleagues of The University of Tokyo, as well as similar materials. The materials exhibiting the third highest transition temperature of 38 K (-235 oC) are Ba1-xKxFe2As2, in which superconductivity was discovered by Johrendt and colleagues in Germany, and Ca10(Pt4As8)(Fe2-xPtxAs2)5, discovered by the scientists of Okayama University in this research.
*4 New direction for the design of novel high-temperature superconductors
A comment from Jun-ichi Shimoyama, an associate professor of superconductivity engineering of the Department of Applied Chemistry, The University of Tokyo, can be seen in the "News and Comments" section of the website of JPSJ: Superconductors with a higher transition temperature may be discovered among compounds with an identical or similar crystal structure to that of Ca10(Pt4As8)(Fe2-xPtxAs2)5.
*5 Most complicated atomic arrangement with the lowest symmetry
Figure 1 shows the atomic arrangement of the new superconductor determined by the synchrotron radiation X-ray diffraction experiment at SPring-8. In this two-dimensional characteristic arrangement, FeAs layers responsible for superconductivity and Ca10(Pt4As8) layers called spacer layers are alternately stacked.
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