Selectively Controlled Ferromagnets by Electric Fields in van der Waals Ferromagnetic Heterojunctions

Abstract

Charge transfer plays a key role at the interfaces of heterostructures, which can affect electronic structures and ultimately the physical properties of the materials. However, charge transfer is difficult to manipulate externally once the interface is formed. The recently discovered van der Waals ferromagnets with atomically sharp interfaces provided a perfect platform for the electrical control of interfacial charge transfer. Here, we report magnetoresistance experiments revealing electrically tunable charge transfer in Fe 3 GeTe 2 /Cr 2 Ge 2 Te 6 /Fe 3 GeTe 2 all-magnetic van der Waals heterostructures, which can be exploited to selectively modify the switching fields of the top or bottom Fe 3 GeTe 2 electrodes. The directional charge transfer from metallic Fe 3 GeTe 2 to semiconducting Cr 2 Ge 2 Te 6 is revealed by first-principles calculations, which remarkably modifies the magnetic anisotropy energy of Fe 3 GeTe 2 , leading to the dramatically suppressed coercivity. The electrically selective control of magnetism demonstrated in this study could stimulate the development of spintronic devices based on van der Waals magnets. KEYWORDS: controllable coercivity, charge transfer, Cr 2 Ge 2 Te 6 , Fe 3 GeTe 2 , van der Waals heterostructure

Recent advances in two-dimensional intrinsic ferromagnetic materials Fe3X(X=Ge and Ga)Te2 and their heterostructures for spintronics

“…Without pinholes in the InSe layer, the vdWHs exhibit a TMR of 41% owing to the Schottky barrier at the interface. Recently, Wang et al also pointed out based on the measurement of the perpendicular magneto-optical Kerr effect and calculations based on first-principles 142 that the magnetic coupling could be ignored at the Fe 3 GeTe 2 /Cr 2 Ge 2 Te 6 interface and that the Fe 3 GeTe 2 /Cr 2 Ge 2 Te 6 /Fe 3 GeTe 2 vdWHs exhibited a tunneling behavior. 142,143 Recently, the discovery of 2D room-temperature FM electrodes sets a milestone in the field of spintronic devices.…”

“…Recently, Wang et al also pointed out based on the measurement of the perpendicular magneto-optical Kerr effect and calculations based on first-principles 142 that the magnetic coupling could be ignored at the Fe 3 GeTe 2 /Cr 2 Ge 2 Te 6 interface and that the Fe 3 GeTe 2 /Cr 2 Ge 2 Te 6 /Fe 3 GeTe 2 vdWHs exhibited a tunneling behavior. 142,143 Recently, the discovery of 2D room-temperature FM electrodes sets a milestone in the field of spintronic devices. In 2023, Chang et al prepared Fe 3 GaTe 2 /MoS 2 /Fe 3 GaTe 2 vdWHs 144 and Fe 3 GaTe 2 /MoSe 2 /Fe 3 GaTe 2 vdWHs 145 and found that although MoS 2 and MoSe 2 are semiconductors, these vdWHs exhibit metallic conducting properties owing to the strong hybridization between MoS 2 or MoSe 2 and the Fe, Ga, or Te atoms of Fe 3 GaTe 2 .…”

“…98 Notably, Wang et al recently found that the switching fields of Fe 3 GeTe 2 can be modified in Fe 3 GeTe 2 /Cr 2 Ge 2 Te 6 /Fe 3 GeTe 2 MTJs by the electrical control of interfacial charge transfer. 101,102 Electric field modulations have profound implications on the magnetism of 2D Fe 3 GeTe 2 , providing valuable insights into the design of magnetoelectronic devices based on 2D FM materials.…”

“…Recently, Wang et al also pointed out based on the measurement of the perpendicular magneto-optical Kerr effect and calculations based on first-principles 142 that the magnetic coupling could be ignored at the Fe 3 GeTe 2 /Cr 2 Ge 2 Te 6 interface and that the Fe 3 GeTe 2 /Cr 2 Ge 2 Te 6 /Fe 3 GeTe 2 vdWHs exhibited a tunneling behavior. 142,143…”

Self-Modulated Magnetism in Two-Dimensional Ferromagnet Fe3GeTe2 Induced by Ambient Effects

“…As an ideal platform to understand 2D magnetism, FGT has shown some fascinating physical phenomena such as the topological Hall effect, magnetic skyrmions, − and quantum criticality . For practical applications, spin–orbit torque (SOT) devices, , spin valves, − and magnetic tunneling junctions − based on FGT have been fabricated successfully, exhibiting prospective application in spintronics.…”