| Co-Investigator(Kenkyū-buntansha) |
IKEDA Naoshi Okayama Universty, Science, Professor (00222894)
SHIMOMURA Susumu Keio University, Science and Engineering, Lecturer (00260216)
OKAWA Kenichi Japan Atomic Energy Agency, J-PARK Center, Researcher (80391332)
MORI Shigeo Osaka Prefecture University, Physical science, Professor (20251613)
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| Budget Amount *help |
¥3,850,000 (Direct Cost: ¥3,700,000、Indirect Cost: ¥150,000)
Fiscal Year 2007: ¥650,000 (Direct Cost: ¥500,000、Indirect Cost: ¥150,000)
Fiscal Year 2006: ¥3,200,000 (Direct Cost: ¥3,200,000)
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| Research Abstract |
We have investigated the crystal structure and the charge order of mixed valence oxide Fe_2BO_4 by synchrotron X ray diffraction, neutron diffraction, ele diffraction, and Mossbauer spectroscopy. Our results are summarized as follows ;
1)Preparation of the specimens : Polycrystalline, polycrystalline containing "B isotope, and single crystal were prepared.
2)Evaluation of the charge order and magnetic structure by Mossbauer spectroscopy : By the quadrupole effect, we examined the reported charge order patten concluded that the pattern or the structure parameters might be wrong. We also examined the magnetic structure by applying external magnetic field a temperatures, and found that the magnetic structure is parasitic one (canted or spiral).
3) Diffraction measurements using polycrystalline : In the synchrotron X ray diffraction, we could not fined superstructure reflections corresponding to the dot of the unit cell along the a-axis. We found, however, an anomalous temperature dependence of the lattice parameters around the transition temperature. C other hand in neutron diffraction, we found some weak superstructure reflections. Assuming a tentative space group, we could see a difference in bond valenci of Fe-O in each Fe site, which may be indicative of a charge order. We also found that the B parameters are elongated along the a-axis.
4)Transmission electron microscope using single crystal : We found at room temperature clear superstructure reflections corresponding to the doubling of th cell along the a-axis. With the increase of temperature, the reflections become incommensurate, and finally disappear.
We are intending to investigate further to determine the space group and the charge order pattern, together with the magnetic structure.
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