Large Tunneling Magnetoresistance in van der Waals Ferromagnet/Semiconductor Heterojunctions

Abstract

2D layered chalcogenide semiconductors have been proposed as a promising class of materials for low‐dimensional electronic, optoelectronic, and spintronic devices. Here, all‐2D van der Waals vertical spin‐valve devices, that combine the 2D layered semiconductor InSe as a spacer with the 2D layered ferromagnetic metal Fe3GeTe2 as spin injection and detection electrodes, are reported. Two distinct transport behaviors are observed: tunneling and metallic, which are assigned to the formation of a pinhole‐free tunnel barrier at the Fe3GeTe2/InSe interface and pinholes in the InSe spacer layer, respectively. For the tunneling device, a large magnetoresistance (MR) of 41% is obtained under an applied bias current of 0.1 µA at 10 K, which is about three times larger than that of the metallic device. Moreover, the tunneling device exhibits a lower operating bias current but a more sensitive bias current dependence than the metallic device. The MR and spin polarization of both the metallic and tunneling devices decrease with increasing temperature, which can be fitted well by Bloch's law. These findings reveal the critical role of pinholes in the MR of all‐2D van der Waals ferromagnet/semiconductor heterojunction devices.

Spin Valve Effect Based on Out‐Of‐Plane Magnetization Electrodes of Pt/Co/Ru with WSe2 and InSe Barriers

“…On the other hand, there may still exist slight pinhole. [ 18 ] So the synergetic effect contributed to the linear I‐V curve, as observed as Pt/Co/Ru/WSe 2 /FGT. We also measured the SV effect of InSe based device, and the MR value can reach to 0.019% at 100 K with 50 μA.…”

“…[8,9] Several efforts have been attempted in the 2D semiconductors-based spin valves (SVs) in both experimental and theoretical efforts. [10][11][12] Structures involving MoS 2 , [13,14] WS 2 , [15,16] WSe 2 , [11] and WTe 2 [17,18] were studied with ferromagnetic (FM) electrodes made of permalloy (Ni 80 Fe 20 ), [11,12] Fe, [19,20] Co, [21,22] Ni, [22] half-metallic CrO 2 , [23] La 0.7 Sr 0.3 MnO 3 , [24] Fe 3 O 4 , [25] and Fe 3 Si. [26] However, the FM electrodes mentioned above all show in-plane magnetic anisotropy.…”

“…[34,35] Among the various kinds of emerging magnetic materials, Fe 3 GeTe 2 (FGT) shows outstanding performances by possessing metallic nature, large PMA, better stability, and relatively high Curie temperature (T c %220 K in bulk and %130 K in monolayer). [36][37][38] Benefiting from the advantages of FGT, the spin valves-based insulator, [35] semi-metal, [34] and semiconductors [14,15,18,39] have been proposed theoretically and verified experimentally. However, there are still some challenges for devices based on FGT, such as the hardness for large-area applications, easy degeneration of ferromagnetic properties in air and T c lower than room temperature, and novel PMA electrodes are strongly desired.…”

Giant magnetoresistance and tunneling electroresistance in multiferroic tunnel junctions with 2D ferroelectrics

“…24 MFTJs based on traditional perovskite ferroelectric materials have the restrictions of critical thickness of ferroelectric films, 25 high contact area resistance 24,[26][27][28][29] and defective nonuniform interface, 30,31 which limit their application in high density microelectronic devices. With the emergence of twodimensional (2D) van der Waals (vdW) materials, 32,33 the MTJ and FTJ based on 2D vdW materials [34][35][36][37][38][39][40][41][42] have attracted great attention as they have atomic thin thickness and perfect interface without dangling bonds. For example, recent theoretical transport calculations show that the Ni/MoS 2 /Ni MTJ displayed TMR ratios of 5.30% and 55.91% when using monolayer and three layer MoS 2 as the tunnelling barrier, respectively.…”

Edge-state-induced magnetism in two-dimensional hematene

“…In particular, for a 2D isotropic Heisenberg magnet with exchange couplings J ij which decay faster than jr i À r j j 2 , the Mermin-Wagner theorem claims that the ferromagnetic phase is hardly preserved above 0 K. 14,15 However, it has been widely recognized that 2D ferromagnetism is of great importance for both fundamental research and practical applications in integration of magnetic materials in functional 2D heterostructures, which are crucial for fabrication of new-generation spintronic and topotronic devices. [16][17][18][19][20][21][22][23][24] Therefore, fabrication of 2D ferromagnetic materials has motivated extensive investigations in recent years. [25][26][27][28][29][30][31][32][33][34] So far, two kinds of mechanisms have been established to break the constraint of Mermin-Wagner theorem in 2D ferromagnetic materials.…”