Physic and Chemistry of Oxygen Holes : Phase Transitions and Dynamics in High-Valence Transition-Metal Oxides

我们在synthesizing single crystalline thin films of perovskite-type oxides srfeo_3cafeo_3 and srfe_ <0.5> co_ <0.5> o_3 containing unusually high valence Fe^<4+> and Co^<4+> ions. Thefilms were fabricated using the laser ablation technique and subsequent ozone. Wediscovered unusual anomalous Hall effect in srfeo_3 thin film Charge disproportionation inperovsfcite-lype Fe oxides were studied using photoemission spectroscopy and Hartree-Fockband-structure calculations.它发现了electron-lattice interaction plays an important角色in the charge disproportionation in cafeo_3 whereas the charge disproportionation occurs purelyelectronically in la_< 1/3> sr_< 2/3> feo_< 3->. Moessbauer measurements of cafeo_3sr_ <2/3> la__ <1/3> feo__ <3-> were made under high pressure in order to study the pressure dependence ofcharge disproportionation and magnetic ordering. We found that 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将3 fe 2 o译文:7,and a triple-layer perovskite lasr_3 fe_3o_< 10> and discovered charge disproportionatian in thesecompounds. We also found helical magnetic ordering in sr_3f_2o_7，and a collinear one in lasr_3 fe_3o_ <10->. Inelastic nuclear resonant scattering of synchrotronradiation was made on cafeo_3 and sr_3 <2/3> la_3 <1/3> feo_3 -> Changes in the Fe local phonon density ofstates were observed across the charge ordering temperature In the measurements of the nuclearresonance scattering from cafeo_3 and sr_2 /3> la_3 <1/3> feo_3，a dramatic change in the intensity of the elastic peak across the magnetic phase transitiondiscovered. Element-selective inelastic nuclear resonance scattering measurements from <161>Dy andFe nuclei were made on perovskite-type dyfeo_ <3->. The local phonon density of states of DyFe thus obtained were compared with shell-model calculations，and the mode assignment was made. By the measurements of magnetic circular dichroism in soft-x-rayabsorption,the electronic and magnetic states of srfe_1 -x> co_xo_3 and their changes induced by Co substitution单一crystals of prno_3 were synthesized under high pressure. It was foundthat across the metal-insulator transitionsymmetry is lowered from orthorhombic to monoclinic. Furthermore，charge disproportionation at the Ni sites were confirmed in the insulating monoclinic phaseTriclinic perovskite prni0_3 was synthesized under high pressure. The Bi atoms at The Asites werefound 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 ofphotoemission results on perovskite-type Ni oxides，我们承诺有两个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

・ 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