[en] We measured the resistivity under pulsed high electric field up to 4000 V/cm in La_1/3Sr_2/3FeO₃ thin film which exhibits charge disproportionation (CD) at 185 K. To eliminate the self-heating effect, we adopted thin films (rather than bulk samples) and micro-fabrication with the focused ion beam technique. Current-voltage characteristics showed non-linear behavior above 1000 V/cm at 170 K; this behavior appears only in CD phase. The threshold field E_th increases as temperature is decreased. Negative differential resistivity and delay in pulse wave form which are characteristic for de-pinned charge density wave were also observed. These suggest an occurrence of collective motion of carriers under CD phase

[en] La_1/3Ca_2/3FeO₃ with unusually-high-valence Fe^3.67+ was synthesized at a high pressure and high temperature. The compound crystallizes in a √2a×2a×√2a perovskite cell in which the La and Ca ions at the A site are disordered. At 217 K the Fe^3.67+ shows charge disproportionation to Fe³⁺ and Fe⁵⁺ in a ratio of 2:1, and this disproportionation is accompanied by transitions in magnetic and transport properties. The charge-disproportionated Fe³⁺ and Fe⁵⁺ are arranged along the <111> direction of the cubic perovskite cell. The local electronic and magnetic environments of Fe in La_1/3Ca_2/3FeO₃ are quite similar to those of Fe in La_1/3Sr_2/3FeO₃, and the 2:1 charge disproportionation pattern of Fe³⁺ and Fe⁵⁺ in La_1/3Ca_2/3FeO₃ is also the same as that in La_1/3Sr_2/3FeO₃. - Graphical abstract: The perovskite-structure oxide La_1/3Ca_2/3FeO₃ with unusually-high-valence Fe^3.67+ shows charge disproportionation to Fe³⁺ and Fe⁵⁺ in a ratio of 2:1, and the charge-disproportionated Fe³⁺ and Fe⁵⁺ are arranged along the <111> direction of the cubic perovskite cell. - Highlights: • La_1/3Ca_2/3FeO₃ with unusually-high-valence Fe^3.67+ was synthesized at a high pressure and high temperature. • At 217 K the Fe^3.67+ shows charge disproportionation (CD) to Fe³⁺ and Fe⁵⁺ in a ratio of 2:1. • The charge-disproportionated Fe³⁺ and Fe⁵⁺ are arranged along the <111> direction of the cubic perovskite cell. • The disproportionation is accompanied by transitions in magnetic and transport properties.

[en] This paper presents an investigation into the relaxation process of photo-excited carriers in anatase TiO₂ thin films, in which the concentration of oxygen vacancy is controlled by annealing at various temperatures in an oxygen atmosphere. The influence of oxygen vacancies on absorption spectra, photoluminescence (PL) spectra, and PL decay dynamics are discussed

[en] Alkali and alkali earth hydrides have been used as solid state reductants recently to yield many interesting new oxygen-deficient transition metal oxides. These reactions have tacitly been assumed to be a solid phase reaction between the reductant and parent oxide. We have conducted a number of experiments with physical separation between the reductant and oxides, and find that in some cases reduction proceeds even when the reagents are physically separated, implying reactions with in-situ generated H₂ and, to a lesser extent, getter mechanisms. Our findings change our understanding of these topochemical reactions, and should enhance the synthesis of additional new oxides and nanostructures. - Graphical abstract: Topochemical reductions with hydrides: Solid state or gas phase reaction? Display Omitted - Highlights: • SrFeO₂ and LaNiO₂ were prepared by topochemical reduction of oxides. • Separating the reducing agent (CaH₂, Mg metal) from the oxide still results in reduction. • Such topochemical reactions can occur in the gas phase