Two-dimensional ferromagnetic superlattices

• 来源期刊: 国家科学评论（英文版）
• 关键词: 2D ferromagnetic material room temperature 2-inch Fe3GeTe2 film wafers proximity effect (Fe3GeTe2/CrSb)n superlattice
• 年，卷（期）: 2020,（4）
• 页码范围: 745-754
• 页数: 10页
• 语种: 英文
• DOI: 10.1093/nsr/nwz205

摘要

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 (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 elemental specific X-ray magnetic circular dichroism (XMCD) measurements,we have unequivocally discovered that TC of4-1ayer Fe3GeTe2 can be significandy enhanced from 140 K to 230 K because of the interracial 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 inteffacial Cr layer gives rise to the TC enhancement of the Fe3GeTe2 films,in accordance with our XMCD measurements.Strikingly,by introducing rich Fe in a 4-layer FGT/CS superlattice,Tc 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.