Gate-Tuned Interlayer Coupling in van der Waals Ferromagnet Fe3GeTe2 Nanoflakes

Abstract

The weak interlayer coupling in van der Waals (vdW) magnets has confined their application to two dimensional (2D) spintronic devices. Here, we demonstrate that the interlayer coupling in a vdW magnet Fe3GeTe2 (FGT) can be largely modulated by a protonic gate. With the increase of the protons intercalated among vdW layers, interlayer magnetic coupling increases.Due to the existence of antiferromagnetic layers in FGT nanoflakes, the increasing interlayer magnetic coupling induces exchange bias in protonated FGT nanoflakes. Most strikingly, a rarely seen zero-field cooled (ZFC) exchange bias with very large values (maximally up to 1.2 kOe) has been observed when higher positive voltages (Vg ≥ 4.36 V) are applied to the protonic gate, which clearly demonstrates that a strong interlayer coupling is realized by proton intercalation. Such strong interlayer coupling will enable a wider range of applications for vdW magnets. .

Gate-Controlled Magnetic Phase Transition in a van der Waals Magnet Fe5GeTe2

“…For vdW itinerant magnet, however, conventional electricfield gating is stumbling in the electrical control of the FM, since the electric field tends to be screened within few nano-meters. Up to date, gate-induced Lithium ion doping (3) and protonic intercalation (41) have been proved to be effective ways to tune the magnetism and interlayer coupling in vdW itinerant magnet FGT. Using the same protonic gate technique, as illustrated in Fig.…”

Observation of plateau-like magnetoresistance in twisted Fe3GeTe2/Fe3GeTe2 junction

“…In principle, two ferromagnetic metals will not work because they will be strongly coupled with no spacer. However, the vdW gap in the twisted FGT/FGT homojunction could decouple two ferromagnetic layers by much weakening the interlayer coupling [24]. Such weak interlayer coupling between two ferromagnetic layers could help to form different coercivity and stabilize the antiparallel magnetic states, eventually generating the PMR effect.…”

Gigantic Current Control of Coercive Field and Magnetic Memory Based on Nanometer‐Thin Ferromagnetic van der Waals Fe3GeTe2

“…It implies that the SOT effect in FGT amounts to the magnetic anisotropy change, whereas such an interpretation is not possible for the damping‐like SOT in other systems. This structure of f SOT derived for a monolayer FGT is also applicable to each layer of a multilayer FGT like our samples since each layer satisfies the symmetries, and the interlayer coupling is weak in the vdW FGT [ 30,31 ] (see more details in the Note S3, Supporting Information). Together with the inherent free energy density that describes the Ising‐type perpendicular magnetic anisotropy of FGT, one obtains the effective free energy density f eff = f 0 + f SOT in the presence of current as follows: where the angles θ and ϕ specify the directions of the unit vector m = (sinθ cosϕ, sinθ sinϕ, cosθ), and J = J (cosϕ J , sinϕ J , 0).…”