Near-room temperature ferromagnetic insulating state in highly distorted LaCoO2.5 with CoO5 square pyramids.

Autor: 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
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Zdroj: Nature Communications; 3/25/2021, Vol. 12 Issue 1, p1-7, 7p
Abstrakt: 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. [ABSTRACT FROM AUTHOR]
Databáze: Complementary Index
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