低温トポタクティック反応による新規機能性遷移金属酸化物の合成と構造物性評価

昨年度より発展的にペロブスカイト構造化合物を中心に研究を展開してきた。特に異常高原子価Feイオンを含む酸化物で、逐次的に電荷不均化と電荷移動という2つの転移が起こる新物質の合成に成功し、特に電荷不均化した状態において、アイドルスピンを有する極めて特異な磁気構造が現れることを見出した。一連の発見は、Feの異常高原子価電子状態の不安定性が新たな形で解消されるとともに、電荷転移が特異な磁気構造を安定化させていることを明らかにした点でも重要である。This year's work has focused on the synthesis and characterization of cation ordered and/or charge transition oxides using high pressure and low temperature, topochemical methods. Notable results include the elucidation of unusual charge behavior in Ca0.5Bi0.5FeO3 displaying charge disproportionation and intermetallic charge transfer transitions, results which have been published in Angewandte Chemie International Edition and in a forthcoming publication submitted to Physical Review Letters.On the unusual charge behavior in Ca0.5Bi0.5FeO3, A-site cation substitution leads to small changes in the structure but large effects on the resulting material properties (eg Sr0.5Bi0.5FeO3 does not show charge ordering or charge transfer). A-site substitution of RE cations for Ca in CaFeO3 allows for an investigation of the role of structure on the charge disproportionation behavior. A large amount of data was collected during a recent neutron diffraction experiment and analysis is ongoing.

昨年度より発展的にペロブスカイト構造化合物を中心に研究を展開してきた。特に異常高原子価Feイオンを含む酸化物で、逐次的に電荷不均化と電荷移動という2つの転移が起こる新物質の合成に成功し、特に電荷不均化した状態において、アイドルスピンを有する極めて特異な磁気構造が現れることを見出した。一連の発見は、Feの異常高原子価電子状態の不安定性が新たな形で解消されるとともに、電荷転移が特異な磁気構造を安定化させていることを明らかにした点でも重要である。This year's work has focused on the synthesis and characterization of cation ordered and/or charge transition oxides using high pressure and low temperature, topochemical methods. Notable results include the elucidation of unusual charge behavior in Ca0.5Bi0.5FeO3 displaying charge disproportionation and intermetallic charge transfer transitions, results which have been published in Angewandte Chemie International Edition and in a forthcoming publication submitted to Physical Review Letters.On the unusual charge behavior in Ca0.5Bi0.5FeO3, A-site cation substitution leads to small changes in the structure but large effects on the resulting material properties (eg Sr0.5Bi0.5FeO3 does not show charge ordering or charge transfer). A-site substitution of RE cations for Ca in CaFeO3 allows for an investigation of the role of structure on the charge disproportionation behavior. A large amount of data was collected during a recent neutron diffraction experiment and analysis is ongoing.