| Co-Investigator(Kenkyū-buntansha) |
SETO Makoto Kyoto University, Research Reactor Institute, Assistant Professor, 原子炉実験所, 助教授 (40243109)
NASU Saburo Osaka University, Faculty of Engineering Science, Professor, 大学院・基礎工学研究科, 教授 (00030057)
TAKANO Mikio Kyoto University, The Institute for Chemical Research, Professor, 化学研究所, 教授 (70068138)
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| Research Abstract |
・ We have succeeded in synthesizing single crystalline thin films of perovskite-type oxides SrFeO_3, CaFeO_3 and SrFe_<0.5>Co_<0.5>O_3 containing unusually high valence Fe^<4+> and Co^<4+> ions. The films were fabricated using the laser ablation technique and subsequent oxidation using ozone. We discovered unusual anomalous Hall effect in SrFeO_3 thin film
・ Charge disproportionation in perovsfcite-lype Fe oxides were studied using photoemission spectroscopy and Hartree-Fock band-structure calculations. It was found that electron-lattice interaction plays an important role in the charge disproportionation in CaFeO_3 whereas the charge disproportionation occurs purely electronically in La_<1/3>Sr_<2/3>FeO_<3->.
・ Moessbauer measurements of CaFeO_3 Sr_<2/3>La_<1/3>FeO_<3-> were made under high pressure in order to study the pressure dependence of charge disproportionation and magnetic ordering. We found that under high pressure, Sr_<2/3>La_<1/3>FeO_<3-> becomes a ferromagnet with a high Cu
… More
rie temperature.
・ We performed Moessbauer measurements on a double-layer perovskite Sr_3Fe_2O_7, and a triple-layer perovskite LaSr_3Fe_3O_<10> and discovered charge disproportionatian in these compounds. We also found helical magnetic ordering in Sr_3Fe_2O_7, and a collinear one in LaSr_3Fe_3O_<10->.
・ Inelastic nuclear resonant scattering of synchrotron radiation was made on CaFeO_3 and Sr_<2/3>La_<1/3>FeO_<3-> Changes in the Fe local phonon density of states were observed across the charge ordering temperature.
・ In the measurements of the nuclear resonance scattering from CaFeO_3 and Sr_<2/3>La_<1/3>FeO_3, a dramatic change in the intensity of the elastic peak across the magnetic phase transition was discovered.
・ Element-selective inelastic nuclear resonance scattering measurements from ^<161>Dy and ^<57>Fe nuclei were made on perovskite-type DyFeO_<3->. The local phonon density of states of Dy and Fe thus obtained were compared with shell-model calculations, and the mode assignment was made.
・ By the measurements of magnetic circular dichroism in soft-x-ray absorption, the electronic and magnetic states of SrFe_<1-x>Co_xO_3 and their changes induced by Co substitution were identified.
・ Single crystals of PrNiO_3 were synthesized under high pressure. It was found that across the metal-insulator transition, the symmetry is lowered from orthorhombic to monoclinic. Furthermore, charge disproportionation at the Ni sites were confirmed in the insulating monoclinic phase.
・ Triclinic perovskite PrNi0_3 was synthesized under high pressure. The Bi atoms at the Asites were found to charge-disproportinate into Bi^<3+> and Bi^<5+>. We found that, when La^<3+> ions were substituted for the Bi ions, a metal-insulator transition occurred as a function of atomic composition.
・ On the basis of photoemission results on perovskite-type Ni oxides, we proposed that there are two kinds of metallic states within the well-known metallic phase, namely, the conventional Pauli-paramagnetic phase and the Curie-Weiss paramagnetic phase with a peudogap. Less
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