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The long-standing scientific mystery of more than 100 years in Invar effect is to be revealed.
-Discovery of local lattice distortion in a giant negative thermal expansion material-
Nov. 18, 2008
Nanomaterials synthesis group (Dr. Shamoto GL) at Neutron Materials Research Center in Quantum Beam Science Directorate of Japan Atomic Energy Agency (President Toshio Okazaki), Prof. Takagi group in RIKEN (President Ryoji Noyori), and Prof. Takigawa group at ISSP in the University of Tokyo (President Hiroshi Komiyama) have discovered lattice distortion accompanied by local Mn6N octahedral rotation in the largest negative thermal expansion material Mn3Cu1-xGexN at room temperature by pulsed neutron powder diffraction and nuclear magnetic resonance measurements.
In general, materials expand with heating, but some do not. As one of well-known examples, there is an Invar alloy (Ni36%, Fe64%) discovered by Charles Edouard Guillaume in 1897. He received the Nobel Prize in physics in 1920 for this discovery.
The mechanism of the Invar effect has been a mystery in more than 100 years since the discovery. In order to reveal it, these research groups have studied this negative thermal expansion material Mn3Cu1-xGexN, resulting in the discovery of the local rotational lattice distortion of Mn6N octahedron. They revealed that this local lattice distortion is closely related to the long-standing scientific mystery for the first time.
This work was performed under the NIMS-RIKEN-JAEA Cooperative Research Program on Quantum Beam Science and Technology contracted on December 18, 2006. This work is partly supported by NEDO, and published in Phys. Rev. Lett. 101 (2008) 205901 (It was also published online on November 14, 2008).
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