Gate-Tuned Interlayer Coupling in van der Waals Ferromagnet Fe$_3$GeTe$_2$ Nanoflakes

TL;DR

This study demonstrates that protonic gating can significantly modulate interlayer magnetic coupling in Fe$_3$GeTe$_2$ nanoflakes, inducing exchange bias and enabling new applications in 2D spintronics.

Contribution

It introduces a protonic gating method to control interlayer coupling in vdW ferromagnets, a novel approach for tuning magnetic properties.

Findings

Proton intercalation increases interlayer magnetic coupling.

Protonation induces exchange bias with large values up to 1.2 kOe.

Zero-field cooled exchange bias observed at high positive voltages.

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 Fe$_3$GeTe$_2$ (FGT) can be largely modulated by a protonic gate.With the increase of the protons intercalated among vdW layers,interlayer magnetic coupling increases.Because of 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.