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Journal Articles

Topotactic synthesis and crystal structure of a highly fluorinated Ruddlesden-Popper-type iron oxide, Sr$$_{3}$$Fe$$_{2}$$O$$_{5+x}$$F$$_{2-x}$$ (x $${approx}$$ 0.44)

Tsujimoto, Yoshihiro*; Yamaura, Kazunari*; Hayashi, Naoaki*; Kodama, Katsuaki; Igawa, Naoki; Matsushita, Yoshitaka*; Katsuya, Yoshio*; Shirako, Yuichi*; Akaogi, Masaki*; Muromachi, Eiji*

Chemistry of Materials, 23(16), p.3652 - 3658, 2011/08

 Times Cited Count:26 Percentile:59.91(Chemistry, Physical)

Topotactic reaction of the Ruddlesden-Popper phase Sr$$_{3}$$Fe$$_{2}$$O$$_{7-delta}$$ ($$delta$$ $${approx}$$ 0.18) with polytetrafluoroethylene yields a highly fluorinated phase Sr$$_{3}$$Fe$$_{2}$$O$$_{5+x}$$F$$_{2-x}$$ (x $${approx}$$ 0.44), compared with Sr$$_{3}$$Fe$$_{2}$$O$$_{6}$$F$$_{0.87}$$ prepared by the reaction of Sr$$_{3}$$Fe$$_{2}$$O$$_{6}$$ and F$$_{2}$$ gas. Structure analyses based on powder neutron diffraction, synchrotron powder diffraction, and $$^{57}$$Fe M$"o$ssbauer spectroscopy measurements demonstrate that the new oxyfluoride perovskite has no anion deficiencies and adopts the tetragonal structure (space group ${it I}$4/${it mmm}$) with lattice constants ${it a}$ = 3.87264(6) ${AA}$ and ${it c}$ = 21.3465(6) ${AA}$ at room temperature. The fluoride ions preferentially occupy the terminal apical anion sites with oxide ions in a disordered manner, which results in square pyramidal coordination around iron.

Journal Articles

Crystal and magnetic structures and properties of BiMnO$$_{3+delta}$$

Belik, A. A.*; Kodama, Katsuaki; Igawa, Naoki; Shamoto, Shinichi; Kosuda, Kosuke*; Muromachi, Eiji*

Journal of the American Chemical Society, 132(23), p.8137 - 8144, 2010/05

 Times Cited Count:49 Percentile:74.59(Chemistry, Multidisciplinary)

Journal Articles

Local crystal structure of multiferroic system BiMnO$$_3$$ by atomic pair distribution function analysis

Kodama, Katsuaki; Iikubo, Satoshi; Shamoto, Shinichi; Belik, A. A.*; Muromachi, Eiji*

Journal of the Physical Society of Japan, 76(12), p.124605_1 - 124605_7, 2007/12

 Times Cited Count:23 Percentile:71.06(Physics, Multidisciplinary)

Journal Articles

Origin of the monoclinic-to-monoclinic phase transition and evidence for the centrosymmetric crystal structure of BiMnO$$_3$$

Belik, A. A.*; Iikubo, Satoshi; Yokosawa, Tadahiro*; Kodama, Katsuaki; Igawa, Naoki; Shamoto, Shinichi; Azuma, Masaki*; Takano, Mikio*; Kimoto, Koji*; Matsui, Yoshio*; et al.

Journal of the American Chemical Society, 129(4), p.971 - 977, 2007/01

 Times Cited Count:182 Percentile:95.3(Chemistry, Multidisciplinary)

Structural properties of polycrystalline single-phased BiMnO$$_3$$ samples prepared at 6 GPa and 1383 K have been studied by selected area electron diffraction (SAED), convergent beam electron diffraction (CBED), and the Rietveld method using neutron diffraction data measured at 300 and 550 K. The SAED and CBED data showed that BiMnO$$_3$$ crystallizes in the centrosymmetric space group C2/c at 300 K. The analysis of Mn-O bond lengths suggested that the orbital order present in BiMnO$$_3$$ at 300 K melts above T= 474 K. The phase transition at 474 K is of the first order and accompanied by a jump of magnetization and small changes of the effective magnetic moment and Weiss temperature.

Journal Articles

Possible unconventional superconductivity and weak magnetism in Na$$_x$$CoO$$_2$$$$cdot$$yH$$_2$$O probed by $$mu$$SR

Higemoto, Wataru; Oishi, Kazuki; Koda, Akihiro*; Kadono, Ryosuke*; Sakurai, Hiroya*; Takada, Kazunori*; Muromachi, Eiji*; Sasaki, Takayoshi*

Physica B; Condensed Matter, 374-375, p.274 - 277, 2006/03

 Times Cited Count:6 Percentile:31.23(Physics, Condensed Matter)

no abstracts in English

Journal Articles

Neutron powder diffraction study on the crystal and magnetic structures of BiCoO$$_3$$

Belik, A. A.*; Iikubo, Satoshi; Kodama, Katsuaki; Igawa, Naoki; Shamoto, Shinichi; Niitaka, Seiji*; Azuma, Masaki*; Shimakawa, Yuichi*; Takano, Mikio*; Izumi, Fujio*; et al.

Chemistry of Materials, 18(3), p.798 - 803, 2006/02

 Times Cited Count:278 Percentile:98.63(Chemistry, Physical)

The crystal and magnetic structures of polycrystalline BiCoO$$_3$$ have been determined by the Rietveldmethod from neutron diffraction data measured at temperatures from 5 to 520 K. BiCoO$$_3$$ (space groupP4mm; Z=1; a=3.72937(7) ${AA}$ and c=4.72382(15) ${AA}$ at room temperature; tetragonality c/a=1.267) is isotypic with BaTiO$$_3$$ and PbTiO$$_3$$ in the whole temperature range. BiCoO$$_3$$ is an insulator with a Neeltemperature of 470 K. A possible model for antiferromagnetic order is proposed with a propagationvector of k=(1/2, 1/2, 0). In this model, magnetic moments of Co$$^{3+}$$ ions are parallel to the c directionand align antiferromagnetically in the ab plane. The antiferromagnetic ab layers stack ferromagneticallyalong the c axis, forming a C-type antiferromagnetic structure. Refined magnetic moments at 5 and 300K are 3.24(2)$$mu$$$$_B$$ and 2.93(2)$$mu$$$$_B$$, respectively. The structure refinements revealed no deviation fromstoichiometry in BiCoO$$_3$$. BiCoO$$_3$$ decomposed in air above 720 K to give Co$$_3$$O$$_4$$ and sillenite-like Bi$$_{25}$$CoO$$_{39}$$.

Journal Articles

BiScO$$_3$$: Centrosymmetric BiMnO$$_3$$-type oxide

Belik, A. A.*; Iikubo, Satoshi; Kodama, Katsuaki; Igawa, Naoki; Shamoto, Shinichi; Maie, Makoto*; Nagai, Takuro*; Matsui, Yoshio*; Stefanovich, S. Y.*; Lazoryak, B. I.*; et al.

Journal of the American Chemical Society, 128(3), p.706 - 707, 2006/01

 Times Cited Count:114 Percentile:89.99(Chemistry, Multidisciplinary)

The crystal structure of BiScO$$_3$$ have been determined by neutron diffraction and electron diffraction measurements. All experimental results shows space group of BiScO$$_3$$ is C2/c, which has a center of symmetry.

Oral presentation

Topotactic synthesis and crystal structure of a fluorinated layered iron oxyfluoride

Tsujimoto, Yoshihiro*; Yamaura, Kazunari*; Matsushita, Yoshitaka*; Muromachi, Eiji*; Hayashi, Naoaki*; Kodama, Katsuaki; Igawa, Naoki; Shirako, Yuichi*; Akaogi, Masaki*

no journal, , 

Topotactic reaction of the n = 2 Ruddlesden-Popper phase Sr$$_{3}$$Fe$$_{2}$$O$$_{7-delta}$$ with the Teflon polymer yields a highly fluorinated phase Sr$$_{3}$$Fe$$_{2}$$O$$_{5+x}$$O$$_{2-x}$$ (x $$sim$$ 0.44). The crystal/magnetic structures and anion composition are determined by a combination of neutron diffraction and $$^{57}$$Fe M$"o$ssbauer spectroscopy experiments. Fluoride anions selectively occupy the terminal apical anion sites, leading to the square pyramidal coordination around the Fe metal center. The oxyfluoride material adopts a simple antiferromagnetic ordered structure with k = (1/2 1/2 0) below 390 K.

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