[Paper Review] Van der Waals Magnet based Spin-Valve Devices at Room Temperature

Bing Zhao, Roselle Ngaloy+4 more|arXiv (Cornell University)|Jul 1, 2021

2D Materials and Applications27 references4 citations

TL;DR

This study demonstrates the first room-temperature spin-valve devices based on van der Waals (vdW) magnets, using Fe5GeTe2/graphene heterostructures. It achieves a large negative tunnel spin polarization of ~45% at room temperature, enabling electrical spin injection, transport, precession, and detection in a lateral device geometry, paving the way for all-2D spintronic circuits at ambient conditions.

ABSTRACT

The discovery of van der Waals (vdW) magnets opened up a new paradigm for condensed matter physics and spintronic technologies. However, the operations of active spintronic devices with vdW magnets are so far limited to cryogenic temperatures, inhibiting its broader practical applications. Here, for the first time, we demonstrate room temperature spin-valve devices using vdW itinerant ferromagnet Fe5GeTe2 in heterostructures with graphene. The tunnel spin polarization of the Fe5GeTe2/graphene vdW interface is detected to be significantly large ~ 45 % and negative at room temperature. Lateral spin-valve device design enables electrical control of spin signal and realization of basic building blocks for device application such as efficient spin injection, transport, precession, and detection functionalities. Furthermore, measurements with different magnetic orientations provide unique insights into the magnetic anisotropy of Fe5GeTe2 and its relation with spin polarization and dynamics in the heterostructure. These findings open opportunities for the applications of vdW magnet-based all-2D spintronic devices and integrated spin circuits at ambient temperatures.

Motivation & Objective

• To overcome the limitation of vdW magnet-based spintronic devices operating only at cryogenic temperatures.
• To demonstrate functional spin-valve devices using van der Waals itinerant ferromagnet Fe5GeTe2 at room temperature.
• To achieve efficient electrical spin injection, transport, precession, and detection in a lateral device architecture.
• To investigate the magnetic anisotropy of Fe5GeTe2 and its impact on spin polarization and dynamics in heterostructures.
• To enable practical applications of all-2D spintronic devices and integrated spin circuits at ambient temperature.

Proposed method

• Fabrication of lateral spin-valve devices using Fe5GeTe2 as the magnetic channel and graphene as the spin transport channel.
• Use of van der Waals heteroepitaxy to form Fe5GeTe2/graphene interfaces with high-quality tunneling characteristics.
• Electrical measurement of spin signal via spin injection and detection using ferromagnetic contacts at room temperature.
• Application of external magnetic fields with varying orientations to probe magnetic anisotropy and spin polarization.
• Measurement of spin precession and spin lifetime under different magnetic configurations to extract spin dynamics.
• Use of tunnel spin polarization analysis to quantify the degree of spin injection efficiency at room temperature.

Experimental results

Research questions

• RQ1 Can van der Waals magnet-based spin-valve devices operate effectively at room temperature?
• RQ2 What is the magnitude and sign of tunnel spin polarization at the Fe5GeTe2/graphene interface at room temperature?
• RQ3 How does the magnetic anisotropy of Fe5GeTe2 influence spin polarization and spin transport in the heterostructure?
• RQ4 Can lateral spin-valve geometry support all key functionalities: injection, transport, precession, and detection of spin signals at room temperature?
• RQ5 What are the implications of these results for the development of all-2D spintronic integrated circuits?

Key findings

• The tunnel spin polarization at the Fe5GeTe2/graphene interface reaches ~45% at room temperature, with a negative sign, indicating strong spin filtering.
• Room-temperature operation of lateral spin-valve devices is successfully demonstrated, enabling electrical control of spin signals.
• The devices exhibit all essential functionalities: efficient spin injection, transport, precession, and detection in a single all-2D heterostructure.
• Magnetic anisotropy measurements reveal a strong correlation between the magnetic orientation of Fe5GeTe2 and its spin polarization and dynamics.
• The results establish Fe5GeTe2 as a viable candidate for room-temperature spintronic applications due to its high spin polarization and robustness at ambient conditions.
• This work marks a critical step toward scalable, all-2D spintronic circuits operating at room temperature.