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Two-dimensional ferromagnetic superlattices

DOI: 10.1093/nsr/nwz205 DOI Help

Authors: Shanshan Liu (Fudan University) , Ke Yang (Fudan University) , Wenqing Liu (Royal Holloway, University of London) , Enze Zhang (Fudan University) , Zihan Li (Fudan University) , Xiaoqian Zhang (Nanjing University) , Zhiming Liao (The University of Queensland) , Wen Zhang (National University of Singapore) , Jiabao Sun (Royal Holloway, University of London) , Yunkun Yang (Fudan University) , Han Gao (The University of Queensland) , Ce Huang (Fudan University) , Linfeng Ai (Fudan University) , Ping Kwan Johnny Wong (National University of Singapore) , Andrew Thye Shen Wee (National University of Singapore) , Alpha T N’diaye (Lawrence Berkeley National Laboratory) , Simon A. Morton (Lawrence Berkeley National Laboratory) , Xufeng Kou (ShanghaiTech University) , Jin Zou (The University of Queensland) , Yongbing Xu (University of York) , Hua Wu (Fudan University) , Faxian Xiu (Fudan University; Collaborative Innovation Center of Advanced Microstructures)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: National Science Review

State: Published (Approved)
Published: December 2019
Diamond Proposal Number(s): 20748

Open Access Open Access

Abstract: Mechanically-exfoliated two-dimensional ferromagnetic materials (2D FMs) were discovered to possess long-range ferromagnetic order and topologically nontrivial skyrmions in few-layers. However, owing to the dimensionality effect, such few-layer systems usually exhibit much lower Curie temperature (TC) compared to their bulk counterparts. It is therefore of great interest to explore effective approaches to enhance their TC, particularly in wafer-scale for practical applications. Here, we report an interfacial proximity-induced high-TC 2D FM Fe3GeTe2 (FGT) via A-type antiferromagnetic material CrSb (CS) which strongly couples to FGT. A superlattice structure of (FGT/CS)n, where n stands for the period of FGT/CS heterostructure, has been successfully produced with sharp interfaces by molecular-beam epitaxy on 2-inch wafers. By performing the elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally discovered that TC of 4-layer Fe3GeTe2 can be significantly enhanced from 140 K to 230 K because of the interfacial ferromagnetic coupling. In the meanwhile, an inverse proximity effect occurs in the FGT/CS interface, driving the interfacial antiferromagnetic CrSb into a ferrimagnetic state as evidenced by a double-switching behavior in hysteresis loops and the XMCD spectra. Density functional theory calculations show that the Fe-Te/Cr-Sb interface is strongly FM coupled and doping of the spin-polarized electrons by the interfacial Cr layer gives rise to the TC enhancement of the Fe3GeTe2 films, in accordance with our XMCD measurements. Strikingly, by introducing rich Fe in 4-layer FGT/CS superlattice, TC can be further enhanced to near room temperature. Our results provide a feasible approach in enhancing the magnetic order of few-layer 2D FMs in wafer-scale and render opportunities for realizing realistic ultra-thin spintronic devices.

Journal Keywords: 2D ferromagnetic material; room temperature; 2-inch Fe3GeTe2 film wafers; proximity effect; (Fe3GeTe2/CrSb)n superlattice

Diamond Keywords: Spintronics; Ferromagnetism

Subject Areas: Materials, Physics

Instruments: I10-Beamline for Advanced Dichroism

Added On: 16/01/2020 10:07


Discipline Tags:

Surfaces Quantum Materials Hard condensed matter - electronic properties Physics Electronics Magnetism Materials Science interfaces and thin films

Technical Tags:

Spectroscopy Circular Dichroism (CD) X-ray Magnetic Circular Dichroism (XMCD)