Wafer-scale two-dimensional ferromagnetic Fe3GeTe2 thin films grown by molecular beam epitaxy

Shanshan Liu,Cheng Zhang,Kaiyou Wang,Yanwen Liu,Jin Zou,Enze Zhang,Xiang Yuan,Weiyi Wang,Jiwei Ling,Yu Sheng,Ce Huang,Yichao Zou,Faxian Xiu

doi:10.1038/s41699-017-0033-3

Abstract

Recently, layered two-dimensional ferromagnetic materials (2D FMs) have attracted a great deal of interest for developing low-dimensional magnetic and spintronic devices. Mechanically exfoliated 2D FMs were discovered to possess ferromagnetism down to monolayer. It is therefore of great importance to investigate the distinct magnetic properties at low dimensionality. Here, we report the wafer-scale growth of 2D ferromagnetic thin films of Fe3GeTe2 via molecular beam epitaxy, and their exotic magnetic properties can be manipulated via the Fe composition and the interface coupling with antiferromagnetic MnTe. A 2D layer-by-layer growth mode has been achieved by in situ reflection high-energy electron diffraction oscillations, yielding a well-defined interlayer distance of 0.82 nm along {002} surface. The magnetic easy axis is oriented along c-axis with a Curie temperature of 216.4 K. Remarkably, the Curie temperature can be enhanced when raising the Fe composition. Upon coupling with MnTe, the coercive field dramatically increases 50% from 0.65 to 0.94 Tesla. The large-scale layer-by-layer growth and controllable magnetic properties make Fe3GeTe2 a promising candidate for spintronic applications. It also opens up unprecedented opportunities to explore rich physics when coupled with other 2D superconductors and topological matters.

Highlights

Two approaches are currently adopted involving the introduction of defects or adatoms into parent materials or the proximity effect with ferromagnetic materials,[18] for instance, the ferromagnetism in NbSe2 through hydrogen absorbed on the surface,[19] and the search for the intrinsic magnetic materials
Through previous ferromagnetic resonance (FMR) study,[17] the exfoliated CrGeTe3 exhibits a Curie temperature around 61 K with an uniaxial magnetic property which can be tuned by external magnetic field.[27]
The ferromagnetic single crystals such as Fe3GeTe2 and CrGeTe3 were mainly developed by chemical vapor transport (CVT).[17, 25]

Summary

Introduction

With the discovery of graphene and its astonishing physical properties,[1] a new class of two-dimensional (2D) materials, ascribed to the dimensionality effect and modulation in their band structures, has become the focus of intense research which ranges from 2D semiconductors, like black phosphorous,[2] MoS2,3 and WSe2,4–6 to 2D superconductors, for example, NbSe2,7, 8 and FeSe.[9,10,11] The 2D ferromagnetic materials (2D FMs),[12] were predicted to have promising spintronic applications[13,14,15,16] with stable storage, faster response and low-power dissipation.[12, 17] To this end, two approaches are currently adopted involving the introduction of defects or adatoms into parent materials or the proximity effect with ferromagnetic materials,[18] for instance, the ferromagnetism in NbSe2 through hydrogen absorbed on the surface,[19] and the search for the intrinsic magnetic materials.the resulting ferromagnetic materials by the former method significantly suffer from the undesired stability and limited controllability. To explore low-temperature electrical properties, two-inch Fe3GeTe2 films were cut into small pieces and fabricated into a Hall-bar structure (Fig. 2a inset).

Results

Conclusion