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- Title
Near-room temperature ferromagnetic insulating state in highly distorted LaCoO2.5 with CoO5 square pyramids.
- Authors
Zhang, Qinghua; Gao, Ang; Meng, Fanqi; Jin, Qiao; Lin, Shan; Wang, Xuefeng; Xiao, Dongdong; Wang, Can; Jin, Kui-juan; Su, Dong; Guo, Er-Jia; Gu, Lin
- Abstract
Dedicated control of oxygen vacancies is an important route to functionalizing complex oxide films. It is well-known that tensile strain significantly lowers the oxygen vacancy formation energy, whereas compressive strain plays a minor role. Thus, atomic reconstruction by extracting oxygen from a compressive-strained film is challenging. Here we report an unexpected LaCoO2.5 phase with a zigzag-like oxygen vacancy ordering through annealing a compressive-strained LaCoO3 in vacuum. The synergetic tilt and distortion of CoO5 square pyramids with large La and Co shifts are quantified using scanning transmission electron microscopy. The large in-plane expansion of CoO5 square pyramids weaken the crystal field splitting and facilitated the ordered high-spin state of Co2+, which produces an insulating ferromagnetic state with a Curie temperature of ~284 K and a saturation magnetization of ~0.25 μB/Co. These results demonstrate that extracting targeted oxygen from a compressive-strained oxide provides an opportunity for creating unexpected crystal structures and novel functionalities. Here, Zhang et al. succeed in creating a heavily distorted oxygen deficient film of lanthanum cobaltite. The new phase of LaCoO2.5 has several unique properties, most notably, a Curie temperature of 284 K, significantly larger than the films from which it was derived.
- Subjects
CURIE temperature; SCANNING transmission electron microscopy; PYRAMIDS; OXIDE coating
- Publication
Nature Communications, 2021, Vol 12, Issue 1, p1
- ISSN
2041-1723
- Publication type
Article
- DOI
10.1038/s41467-021-22099-y