Above-room-temperature ferromagnetism in ultrathin van der Waals magnet

TL;DR

This paper reports the discovery of ultrathin van der Waals ferromagnetic materials exhibiting stable room-temperature magnetism, with potential applications in spintronics, supported by experimental observations and theoretical predictions.

Contribution

It demonstrates room-temperature ferromagnetism in exfoliated CFGT flakes as thin as 16 nm and predicts high Tc in monolayers through Monte Carlo simulations.

Findings

Room-temperature ferromagnetism observed in 16 nm CFGT flakes.

Curie temperature ranges from 310 K to 328 K.

Monte Carlo simulations predict Tc ~270 K in monolayer CFGT.

Abstract

Two-dimensional (2D) magnetic van der Waals materials provide a powerful platform for studying fundamental physics of low-dimensional magnetism, engineering novel magnetic phases, and enabling ultrathin and highly tunable spintronic devices. To realize high quality and practical devices for such applications, there is a critical need for robust 2D magnets with ordering temperatures above room temperature that can be created via exfoliation. Here the study of exfoliated flakes of cobalt substituted Fe5GeTe2 (CFGT) exhibiting magnetism above room temperature is reported. Via quantum magnetic imaging with nitrogen-vacancy centers in diamond, ferromagnetism at room temperature was observed in CFGT flakes as thin as 16 nm. This corresponds to one of the thinnest room-temperature 2D magnet flakes exfoliated from robust single crystals, reaching a thickness relevant to practical spintronic applications. The Curie temperature Tc of CFGT ranges from 310 K in the thinnest flake studied to 328 K in the bulk. To investigate the prospect of high-temperature monolayer ferromagnetism, Monte Carlo calculations were performed which predicted a high value of Tc ~270 K in CFGT monolayers. Pathways towards further enhancing monolayer Tc are discussed. These results support CFGT as a promising platform to realize high-quality room-temperature 2D magnet devices.