Highly Efficient Nonvolatile Magnetization Switching and Multi‐Level States by Current in Single Van der Waals Topological Ferromagnet Fe₃GeTe₂

Abstract

Robust multi-level spin memory with the ability to write information electrically is a long-sought capability in spintronics, with great promise for applications. Here, nonvolatile and highly energy-efficient magnetization switching is achieved in a single-material device formed of van-der-Waals (vdW) topological ferromagnet Fe 3 GeTe 2 , whose magnetic information can be readily controlled by a tiny current. Furthermore, the switching current density and power dissipation are about 400 and 4000 times smaller than those of the existing spin-orbit-torque magnetic random access memory based on conventional magnet/heavy-metal systems. Most importantly, multi-level states, switched by electrical current are also demonstrated, which can dramatically enhance the information capacity density and reduce computing costs. Thus, the observations combine both high energy efficiency and large information capacity density in one device, showcasing the potential applications of the emerging field of vdW magnets in the field of spin memory and spintronics.

Nonlocal Manipulation of Magnetism in an Itinerant Two-Dimensional Ferromagnet

“…Next, on the basis of recent studies pertaining to current-controlled magnetism in FGT, − we present a primary demonstration of nonlocal magnetism control via current. As shown in Figure , a long FGT strip with a thickness of 20 ± 1 nm was exfoliated and transferred onto a Si/SiO 2 substrate.…”

“…A potential technique is to manipulate the magnetism of local sites nonlocally through in-plane magnetic interactions, which are closely related to the domains. For instance, a recent study pertaining to coercive field modulation in FGT demonstrated that currents can drive domain wall motion in FGT through spin–orbital torque (SOT) and Joule heating. ,− Therefore, the understanding of domain states and domain dynamics in 2D magnets is extremely important. For monolayer CrI 3 , domains can be observed directly via reflected magnetic circular dichroism (RMCD) and second-harmonic generation measurements .…”

Imaging current control of magnetization in Fe$_3$GeTe$_2$ with a widefield nitrogen-vacancy microscope

“…To first demonstrate imaging spintronic effects, we consider current-reduced coercivity, a phenomenon previously observed in FGT and reported to arise from bulk SOTs generated by the injection of currents directly in the FGT flake [9,10]. SOTs are supported in FGT by the broken inversion symmetry within its crystal structure [40,41].…”

“…S2(c)], clearly shows a spatial dependence of the strength of the magnetization which we attribute to areas of different thickness/number of layers. For instance, in the top part of the image the thick (thin) region of the flake with 23 (10) layers is found to have an average areal magnetization density of 50 µ B nm −2 (20 µ B nm −2 ). Assuming each iron ion contributes 1.5 µ B on average (as in bulk FGT at low temperatures [57]), we expect an areal magnetization density of 33 µ B nm −2 per monolayer.…”

“…Furthermore, their freestanding nature facilitates stacking layers of material at different angles to create twisted structures or layering with different materials (heterostructures) to create new interface interactions [4,5]. Exploiting external stimuli and interface interactions are driving the development of new devices based on vdW magnets [5][6][7][8][9][10][11]. An area of significant interest for 2D vdW magnets is spintronics, where external stimulation and interface interactions play an important role in creating a variety of phenomena [11][12][13][14], which primarily involve the interaction between the magnetic structure of a host material and the magnetic moment of injected electrons.…”