Two-dimensional ferromagnetic superlattices. Issue 4 (16th December 2019)

• Record Type: Journal Article
• Authors: Liu, Shanshan; Yang, Ke; Liu, Wenqing; Zhang, Enze; Li, Zihan; Zhang, Xiaoqian; Liao, Zhiming; Zhang, Wen; Sun, Jiabao; Yang, Yunkun; Gao, Han; Huang, Ce; Ai, Linfeng; Wong, Ping Kwan Johnny; Wee, Andrew Thye Shen; N'Diaye, Alpha T; Morton, Simon A; Kou, Xufeng; Zou, Jin; Xu, Yongbing; Wu, Hua; Xiu, Faxian
• Is Part Of: National science review. Volume 7:Issue 4(2020)
• Page Start: 745
• Page End: 754
• Publication Date: 2019-12-16
• Subjects: 2D ferromagnetic material -- room temperature -- 2-inch Fe3GeTe2 film wafers -- proximity effect -- (Fe3GeTe2/CrSb)n superlattice; Science -- Periodicals; 505
• DOI: 10.1093/nsr/nwz205
• Languages: English
• ISSNs: 2095-5138

Abstract

Abstract: Mechanically exfoliated two-dimensional ferromagnetic materials (2D FMs) possess long-range ferromagnetic order and topologically nontrivial skyrmions in few layers. However, because of the dimensionality effect, such few-layer systems usually exhibit much lower Curie temperature ( T C ) compared to their bulk counterparts. It is therefore of great interest to explore effective approaches to enhance their T C, particularly in wafer-scale for practical applications. Here, we report an interfacial proximity-induced high- T C 2D FM Fe3 GeTe2 (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 elemental specific X-ray magnetic circular dichroism (XMCD) measurements, we have unequivocally discovered that T C of 4-layer Fe3 GeTe2 can be significantly enhanced from 140 K to 230 K because of the interfacial ferromagnetic coupling. Meanwhile, an inverse proximity effect occurs in the FGT/CS interface, driving the interfacial antiferromagnetic CrSb into a ferrimagnetic state as evidenced by 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 T C enhancement of the Fe3 GeTe2 films, in accordance with our XMCD measurements. Strikingly, by introducing rich Fe in a 4-layer FGT/CS superlattice, T C can be further enhanced to near room temperature. Our results provide a feasible approach for enhancing the magnetic order of few-layer 2D FMs in wafer-scale and render opportunities for realizing realistic ultra-thin spintronic devices. Abstract : Utilizing proximity effect, we realize an effective and reliable approach to accomplish near-room-temperature (286.7 K) ferromagnetic order and double switching behavior in wafer-scale 4-layer-Fe3 GeTe2 /1.6-nm-CrSb superlattice.