Scientific Highlights : Direct observation of s-electron magnetism
投稿者 : webmaster 投稿日時： 2012-11-20 19:00:00 (4588 ヒット)
Electron has a feature of magnet, so called "spin". In magnetic materials, huge number of electronic spins spontaneously align their directions resulting in "ordered magnetic states". Ordinary magnets typically contain transition elements and/or rare earth elements. In the past decades, great effort has been made to realize the magnetic ordering in materials comprising only nonmagnetic elements. One fascinating example is three dimensionally arrayed alkali-metal nanoclusters in zeolite crystals. Figure (a) shows a schematic illustration of the crystal structure of sodalite which is a kind of zeolites. In sodalite, nano-sized cages are arrayed in a body-centered-cubic structure. We can "dope" a sodium atom into each cage, and an s-electron provided by the guest sodium atom is accommodated in the cage as shown in Fig. (b). Due to an exchange interaction between the adjacent s-electrons through the window of the cage, antiferromagnetic ordering is realized. Recently, we, a group from Osaka University, succeeded in detecting directory the magnetic ordering of this material by using a neutron diffraction for the first time. The experiments were performed using the spectrometer PONTA.The spatial distribution of the s-electron spin was also examined, and it was confirmed that the s-electron delocalized over nanometer size in the cage is responsible for the magnetic ordering. This work is published in Physical Review Letters on 17 Oct. 2012.