Controlling oxygen redox reactions in transition metal oxides offers an attractive route to tune their physical properties; a topotactic structural transformation from their parent phases effectively modifies the electronic state. In this work, infinite-layered SrFeO₂ thin films were produced from brownmillerite SrFeO_2.5 via low-temperature hydro-reduction. After the structural transition, their out-of-plane lattice constants dramatically shrank by ∼12%; tensilely strained samples exhibited metallic character, whereas the compressively strained ones maintained the insulating behavior of their bulk form. According to X-ray linear dichroism results, this strain-mediated electronic anisotropy may be attributed to electron redistribution within degenerated orbitals. This suggests a possible mechanism for the metallic conductivity of infinite-layered SrFeO₂, giving a hint for understanding emergent quantum phenomena, such as the recently discovered superconductivity in nickelates, and stimulating various applications, including in ionic conductivity and oxygen catalysis.

控制过渡金属氧化物中的氧氧化还原反应为调整其物理性质提供了一条有吸引力的途径；来自母相的拓扑结构转变有效地改变了电子状态。在这项工作中，无限层状 SrFeO ₂薄膜是由褐铁矿 SrFeO _2.5制成的通过低温加氢还原。在结构转变之后，它们的面外晶格常数急剧缩小了约 12%；拉伸应变的样品表现出金属特性，而压缩应变的样品保持其块状形式的绝缘性能。根据 X 射线线性二色性结果，这种应变介导的电子各向异性可能归因于简并轨道内的电子重新分布。这暗示了无限层状 SrFeO ₂的金属导电性的可能机制，为理解涌现的量子现象提供了线索，例如最近发现的镍酸盐超导性，并刺激了各种应用，包括离子导电性和氧催化。