Spin-Valve Effect in Fe₃GeTe₂/MoS₂/Fe₃GeTe₂ van der Waals Heterostructures

Abstract

The van der Waals (vdW) materials offer an opportunity to build all-two-dimensional (all-2D) spintronic devices with high-quality interfaces regardless of the lattice mismatch. Here, we report on an all-2D vertical spin valve that combines a typical layered semiconductor MoS 2 with vdW ferromagnetic metal Fe 3 GeTe 2 (FGT) flakes. The linear current−voltage curves illustrate that Ohmic contacts are formed in FGT/MoS 2 interfaces, while the temperature dependence of the junction resistance further demonstrates that the MoS 2 interlayer acts as a conducting layer instead of a tunneling layer. In addition, the magnitude of the magnetoresistance (MR) of 3.1% at 10 K is observed, which is around 8 times larger than that of the reported spin valves based on MoS 2 sandwiched by conventional ferromagnetic electrodes. The MR decreasing monotonically with increasing temperature follows the Bloch's law. As the bias current decreases exponentially, the MR increases linearly up to a maximum value of 4.1%. Our results reveal the potential opportunities of vdW heterostructures for developing novel spintronic devices.

Large Tunneling Magnetoresistance in van der Waals Ferromagnet/Semiconductor Heterojunctions

“…As shown in Figure 4c, the spin polarization P of the tunneling device A decreases from 41 to 13% as the temperature increases from 10 to 210 K. The maximum P is about three times larger than that obtained in other 2D semiconductor‐based spin valves, such as graphene, MoS 2 , or WS 2 ‐based spin valves. [ 12,19,27 ] Similarly, the spin polarization P of the metallic device B decreases from 25.8 to 2.7% (Figure 4d). The estimated temperature dependence of the spin polarization can be fitted well by the Bloch's law, given by P ( T ) = P 0 (1 − αT 3/2 ), in which P 0 is the spin polarization at 0 K and α is a materials‐dependent constant.…”

“…[20,21] Recently, the 2D vdW intrinsic ferromagnetic metal Fe 3 GeTe 2 (FGT) has attracted lots of attention because of its metallic nature, strong perpendicular magnetic anisotropy, and high Curie temperature (T c ) up to 220 K. [22][23][24][25][26] This allows researchers to build up all-2D vdW spin-valve devices with clean interfaces by mechanically exfoliation and dry transfer methods. [27] The FGT-based spin valves with a semiconductor or an insulator as the spacer layer, or even a ferroelectric layer have been proposed theoretically. [28][29][30] Experimentally, the tunneling FGT/ hBN/FGT spin valves have been demonstrated and a high MR of 160% was achieved.…”

Tunable tunneling magnetoresistance in in-plane double barrier magnetic tunnel junctions based on B vacancy h-NB nanoribbons

“…These 2D magnetic materials have great applications in MTJs. For example, van der Waals MTJs with 2D magnetic materials Fe 3 GeTe 2 as the electrode and h-BN 23 or MoS 2 24 as the tunneling barrier were achieved experimentally. Moreover, large tunneling magnetoresistance (TMR) ratios were predicted theoretically for Fe 3 GeTe 2 /graphene/Fe 3 GeTe 2 , 25 Fe 3 GeTe 2 /h-BN/Fe 3 GeTe 2 , 25 CrI 3 /h-BN/CrI 3 , 26 FeCl 2 /MoS 2 /FeCl 2 , 27 1T-CrTe 2 /graphene/1T-CrTe 2 , 28 1T-CrTe 2 /h-BN/1T-CrTe 2 , 28 etc.…”

Current-assisted magnetization reversal in Fe3GeTe2 van der Waals homojunctions

“…The T C is an intrinsic physical quantity and the T C of FGT is around 220 K regardless of its thickness from 8 to 20 nm. 27,37,38 However, the H C is an extrinsic one related to the thickness, geometry and so on. 29 This feature will also make the relationship between the H C and temperature slightly different, which is the reason that the ΔR in our sample broadens at high temperatures (100-160 K).…”