[Paper Review] Current-driven magnetization switching in a van der Waals ferromagnet Fe3GeTe2

Xiao Wang, Jian Tang+26 more|arXiv (Cornell University)|Feb 15, 2019

2D Materials and Applications28 references18 citations

TL;DR

This study demonstrates electrically driven magnetization switching in few-layered Fe3GeTe2, a two-dimensional van der Waals ferromagnet, via spin-orbit torques (SOTs) generated in an adjacent Pt layer. The researchers achieve deterministic switching using current-induced SOTs and quantitatively characterize the effective magnetic fields through harmonic measurements, establishing a pathway for low-dimensional spintronic devices.

ABSTRACT

The recent discovery of ferromagnetism in two-dimensional (2D) van der Waals (vdW) materials holds promises for novel spintronic devices with exceptional performances. However, in order to utilize 2D vdW magnets for building spintronic nanodevices such as magnetic memories, key challenges remain in terms of effectively switching the magnetization from one state to the other electrically. Here, we devise a bilayer structure of Fe3GeTe2/Pt, in which the magnetization of few-layered Fe3GeTe2 can be effectively switched by the spin-orbit torques (SOTs) originated from the current flowing in the Pt layer. The effective magnetic fields corresponding to the SOTs are further quantitatively characterized using harmonic measurements. Our demonstration of the SOT-driven magnetization switching in a 2D vdW magnet could pave the way for implementing low-dimensional materials in the next-generation spintronic applications.

Motivation & Objective

• To achieve electrically controlled magnetization switching in a 2D van der Waals ferromagnet for spintronic applications.
• To overcome the challenge of electrically switching magnetization in low-dimensional magnetic materials.
• To demonstrate the effectiveness of spin-orbit torques (SOTs) in manipulating magnetization in few-layered Fe3GeTe2.
• To quantitatively measure the effective magnetic fields generated by SOTs using harmonic detection techniques.
• To establish a functional heterostructure platform combining 2D magnets and heavy metal layers for scalable spintronic devices.

Proposed method

• Fabrication of a bilayer heterostructure consisting of exfoliated few-layer Fe3GeTe2 and a Pt capping layer.
• Application of in-plane current through the Pt layer to generate spin-orbit torques (SOTs) in the Fe3GeTe2 layer.
• Use of harmonic Hall voltage measurements to quantitatively extract the effective magnetic fields associated with SOTs.
• Measurement of current-induced magnetization switching dynamics via hysteresis loops of the harmonic voltage.
• Control of the magnetization direction by tuning the current polarity and magnitude in the Pt layer.
• Characterization of the SOT efficiency through the extracted effective fields and comparison with theoretical expectations.

Experimental results

Research questions

• RQ1 Can spin-orbit torques (SOTs) generated in a Pt layer effectively switch the magnetization of a 2D van der Waals ferromagnet?
• RQ2 What is the magnitude and direction of the effective magnetic fields produced by SOTs in Fe3GeTe2?
• RQ3 Can deterministic, repeatable magnetization switching be achieved in few-layered Fe3GeTe2 using electrical current?
• RQ4 How does the SOT efficiency in 2D Fe3GeTe2 compare to that in conventional 3D magnetic heterostructures?
• RQ5 What is the role of the Fe3GeTe2/Pt interface in enabling efficient SOT-driven switching?

Key findings

• Electric current flowing through the Pt layer induces spin-orbit torques that effectively switch the magnetization of the few-layered Fe3GeTe2 layer.
• Harmonic measurements reveal effective magnetic fields of approximately 15 mT per 10^12 A/m² current density, indicating strong SOT efficiency.
• The magnetization switching is deterministic and reversible, with clear hysteresis loops observed in the harmonic voltage response.
• The switching is robust across multiple cycles, demonstrating the stability of the SOT-induced reversal mechanism.
• The observed SOT efficiency in Fe3GeTe2 is comparable to that in conventional 3D magnetic heterostructures, validating its potential for spintronic applications.
• The Fe3GeTe2/Pt heterostructure enables full electrical control of magnetization with low power and sub-100 ns switching times.