Significant enhancement of ferromagnetism above room temperature in epitaxial 2D van der Waals ferromagnet Fe_5−δGeTe₂/Bi₂Te₃ heterostructures

Abstract

Two-dimensional (2D) van der Waals (vdW) ferromagnetic metals FexGeTe2 with x = 3 – 5 have raised significant interest in the scientific community. Fe5GeTe2 shows prospects for spintronic applications since...

Large‐Area Synthesis of Ferromagnetic Fe5−xGeTe2/Graphene van der Waals Heterostructures with Curie Temperature above Room Temperature

“…This is, in general, agreement with the value obtained by RHEED, as well as literature values for Fe 5− x GeTe 2 (0 < x ≤ 0.4) bulk crystals [ 7,8,10 ] and thin films. [ 9,13 ]…”

“…[ 7,9,21,39,43 ] Only the transition temperature recently reported for MBE‐grown Fe 5− x GeTe 2 /Bi 2 Te 3 heterostructures ( T C as high as 570 K) surpasses this value. [ 13 ]…”

“…This is, in general, agreement with the value obtained by RHEED, as well as literature values for Fe 5−x GeTe 2 (0 < x ≤ 0.4) bulk crystals [7,8,10] and thin films. [9,13] The intensity modulation along the FGT(11.0) ring exhibits a maximum in the azimuth which is aligned along the SiC[2 1.0] inplane substrate direction. This indicates a preferential in-plane orientation, i.e., the (11.0) net planes of FGT and SiC are parallel, as we previously observed for Fe 3 GeTe 2 films grown on graphene.…”

“…[4,5] In order to enable a broad range of applications, it is critical to identify 2D ferromagnets exhibiting a Curie temperature (T C ) at least at room temperature. [2,6] Among a vast selection of 2D materials with magnetic order investigated recently, [6] the Fe 5−x GeTe 2 (FGT) metallic system (with x usually between 0 and 0.4) [7][8][9][10] has been found to offer a great prospect, as it has been reported to exhibit a T C of around 300 K. [7,10,11] FGT is an itinerant ferromagnetic metal [11] with magnetic properties that can be tuned via electrostatic gating, [12] strain, or doping when interfacing a topological insulator, [13] as well as elemental doping. [14,15] Similar to other 2D Fe-Ge-Te compounds like Fe 3 GeTe 2 [16] and Fe 4 GeTe 2 [17] with below room temperature T C , it possesses a layered structure with each single layer being formed of Fe and Ge 2D slabs encapsulated by layers of Te.…”

“…For this, vdW epitaxy of FGT films on single-crystalline graphene/SiC(0001) templates was realized by molecular beam epitaxy (MBE), a method which has recently been employed for the growth of FGT on substrates such as Al 2 O 3 (0001), WS 2 (001)/Al 2 O 3 (0001), and SrTiO 3 (111). [9,13,21] Importantly, the underlying graphene layers exhibit a sharp interface to the FGT and conserve their high electronic quality, which are key ingredients for the future development of devices in which interfacial effects can be used to control properties and functionalities.…”