Emergent ultra-high temperature ferromagnetism in La2CoO4±x thin films

作者：Ziang Meng, Han Yan, Peixin Qin, Z. G. Yin, Peiheng Jiang, Xiaorong Zhou, Xiaoning Wang, Hongyu Chen, Li Liu, Zhiyuan Duan, Guojian Zhao, Weisheng Zhao, Fengxia Hu, Qinghua Zhang, Zhicheng Zhong, Zhiqi Liu · 发表于：Nano Research · 年份：2024 · DOI：10.1007/s12274-024-6701-7 · 被引用次数：13 · 研究领域：Magnetic and transport properties of perovskites and related materials、Advanced Condensed Matter Physics、Physics of Superconductivity and Magnetism

Searching for novel ferromagnetic oxides with high Curie temperature ( T C ) has been one of the main goals for oxide spintronics. The well-known perovskite cobaltate LaCoO 3 is a classical ferromagnet in its thin-film form; however, it suffers from a low T C (∼ 85 K). Here we report a new type of ferromagnetic La-Co-O films with an ultrahigh T C of ∼ 820 K. They are fabricated by pulsed laser deposition from a LaCoO 3 target at low oxygen partial pressures. Detailed structural analysis indicates that they crystallize in terms of the Ruddlesden–Popper phase of La 2 CoO 4± x . In sharp contrast to the antiferromagnetism of bulk La 2 CoO 4 , the strong ferromagnetism in the La 2 CoO 4± x thin films is firmly demonstrated by magnetometry measurements, X-ray magnetic circular dichroism characterization, and magnetotransport experiments. More importantly, density functional theory calculations indicate that the nonstoichiometric oxygen induces an antiferromagnetic-to-ferromagnetic phase transition, accompanied by the orbital reconstruction of Co 3d electrons. Thus, our study provides an attractive strategy for designing or synthesizing exotic magnetic oxides with high ordering temperatures.