Charge-Transfer-Induced Interfacial Ferromagnetism in Ferromagnet-Free Oxide Heterostructures

Jie Zheng; Wenxiao Shi; Zhe Li; Jing Zhang; Chao-Yao Yang; Zhaozhao Zhu; Mengqin Wang; Jine Zhang; Furong Han; Hui Zhang; Yunzhong Chen; Fengxia Hu; Baogen Shen; Yuansha Chen; Jirong Sun

doi:10.1021/acsnano.4c01910

Charge-Transfer-Induced Interfacial Ferromagnetism in Ferromagnet-Free Oxide Heterostructures

ACS Nano. 2024 Mar 26;18(12):9232-9241. doi: 10.1021/acsnano.4c01910. Epub 2024 Mar 11.

Authors

Jie Zheng^{1

2}, Wenxiao Shi^{1

2}, Zhe Li^{1

2}, Jing Zhang³, Chao-Yao Yang⁴, Zhaozhao Zhu^{1

2}, Mengqin Wang^{1

2}, Jine Zhang⁵, Furong Han⁵, Hui Zhang⁵, Yunzhong Chen^{1

2}, Fengxia Hu^{1

2}, Baogen Shen^{1

2

6}, Yuansha Chen^{1

2}, Jirong Sun^{1

2

7}

Affiliations

¹ Beijing National Laboratory for Condensed Matter Physics and Institute of Physics, Chinese Academy of Sciences, Beijing 100190, People's Republic of China.
² School of Physical Sciences, University of Chinese Academy of Sciences, Beijing 100049, People's Republic of China.
³ Songshan Lake Materials Laboratory, Dongguan, Guangdong 523808, People's Republic of China.
⁴ Department of Materials Science and Engineering, National Yang Ming Chiao Tung University, Hsinchu 300, Taiwan.
⁵ School of Integrated Circuit Science and Engineering, Beihang University, Beijing 100191, People's Republic of China.
⁶ Ningbo Institute of Materials Technology & Engineering, Chinese Academy of Sciences, Ningbo, Zhejiang 315201, People's Republic of China.
⁷ Spintronics Institute, School of Physics and Technology, University of Jinan, Jinan 250022, China.

PMID: 38466082
DOI: 10.1021/acsnano.4c01910

Abstract

Due to the strong interlayer coupling between multiple degrees of freedom, oxide heterostructures have demonstrated exotic properties that are not shown by their bulk counterparts. One of the most interesting properties is ferromagnetism at the interface formed between "nonferromagnetic" compounds. Here we report on the interfacial ferromagnetic phase induced in the superlattices consisting of the two paramagnetic oxides CaRuO₃ (CRO) and LaNiO₃ (LNO). By varying the sublayer thickness in the superlattice period, we demonstrate that the ferromagnetic order has been established in both CaRuO₃ and LaNiO₃ sublayers, exhibiting an identical Curie temperature of ∼75 K. The X-ray absorption spectra suggest a strong charge transfer from Ru to Ni at the interface, triggering superexchange interactions between Ru/Ni ions and giving rise to the emergent ferromagnetic phase. Moreover, the X-ray linear dichroism spectra reveal the preferential occupancy of the d_3z²-r² orbital for the Ru ions and the d_x²-y² orbital for the Ni ions in the heterostructure. This leads to different magnetic anisotropy of the superlattices when they are dominated by CRO or LNO sublayers. This work clearly demonstrates a charge-transfer-induced interfacial ferromagnetic phase in the whole ferromagnet-free oxide heterostructures, offering a feasible way to tailor oxide materials for desired functionalities.

Keywords: CaRuO3; LaNiO3; charge transfer; interfacial ferromagnetism; orbital reconstruction.