Tunable room-temperature ferromagnetism in Co-doped two-dimensional van der Waals ZnO

• Published in: Nature communications 2021-06, Vol.12 (1), p.3952-3952, Article 3952
• Main Authors: Chen, Rui, Luo, Fuchuan, Liu, Yuzi, Song, Yu, Dong, Yu, Wu, Shan, Cao, Jinhua, Yang, Fuyi, N’Diaye, Alpha, Shafer, Padraic, Liu, Yin, Lou, Shuai, Huang, Junwei, Chen, Xiang, Fang, Zixuan, Wang, Qingjun, Jin, Dafei, Cheng, Ran, Yuan, Hongtao, Birgeneau, Robert J., Yao, Jie
• Format: Article
• Language: English
• Subjects: 140/146; 142/126; 147/135; 147/143; 147/28; 147/3; 639/301/119/997; 639/925/357/997; Air temperature; Atomic force microscopy; Carbon dioxide; Circular dichroism; Cobalt; Cobalt oxides; Crystals; Curie temperature; Dichroism; Ferromagnetic materials; Graphene; Humanities and Social Sciences; Kerr magnetooptical effect; Low temperature; Magnetic materials; magnetic properties and materials; Magnetism; MATERIALS SCIENCE; Microscopy; multidisciplinary; Oxides; Room temperature; Science; Science (multidisciplinary); Superconducting quantum interference devices; Transmission electron microscopy; Zinc oxide; Zinc oxides
• ISSN: 2041-1723; 2041-1723
• DOI: 10.1038/s41467-021-24247-w

The recent discovery of ferromagnetism in two-dimensional van der Waals crystals has provoked a surge of interest in the exploration of fundamental spin interaction in reduced dimensions. However, existing material candidates have several limitations, notably lacking intrinsic room-temperature ferromagnetic order and air stability. Here, motivated by the anomalously high Curie temperature observed in bulk diluted magnetic oxides, we demonstrate room-temperature ferromagnetism in Co-doped graphene-like Zinc Oxide, a chemically stable layered material in air, down to single atom thickness. Through the magneto-optic Kerr effect, superconducting quantum interference device and X-ray magnetic circular dichroism measurements, we observe clear evidences of spontaneous magnetization in such exotic material systems at room temperature and above. Transmission electron microscopy and atomic force microscopy results explicitly exclude the existence of metallic Co or cobalt oxides clusters. X-ray characterizations reveal that the substitutional Co atoms form Co 2+ states in the graphitic lattice of ZnO. By varying the Co doping level, we observe transitions between paramagnetic, ferromagnetic and less ordered phases due to the interplay between impurity-band-exchange and super-exchange interactions. Our discovery opens another path to 2D ferromagnetism at room temperature with the advantage of exceptional tunability and robustness. Van der Waals magnetic materials (vdWs) have allowed for the exploration of the two dimensional limit of magnetism, however, most vdWs are only magnetic at low temperature. Herein, the authors overcome this limitation, observing room temperature magnetic ordering in Cobalt doped graphene-like Zinc-Oxide.