Revealing room temperature ferromagnetism in exfoliated Fe${}_5$GeTe${}_2$ flakes with quantum magnetic imaging

Abstract

Van der Waals material Fe${}_5$GeTe${}_2$, with its long-range ferromagnetic ordering near room temperature, has significant potential to become an enabling platform for implementing novel spintronic and quantum devices. To pave the way for applications, it is crucial to determine the magnetic properties when the thickness of Fe5GeTe2 reaches the few-layers regime. However, this is highly challenging due to the need for a characterization technique that is local, highly sensitive, artifact-free, and operational with minimal fabrication. Prior studies have indicated that Curie temperature TC can reach up to close to room temperature for exfoliated Fe${}_5$GeTe${}_2$ flakes, as measured via electrical transport; there is a need to validate these results with a measurement that reveals magnetism more directly. In this work, we investigate the magnetic properties of exfoliated thin flakes of van der Waals magnet Fe${}_5$GeTe${}_2$ via a quantum magnetic imaging technique based on nitrogen vacancy diamond. Through imaging the stray fields, we confirm room-temperature magnetic order in Fe${}_5$GeTe${}_2$ thin flakes with thickness down to 7 units cell. The stray field patterns and their response to magnetizing fields with different polarities point to a perpendicular easy-axis anisotropy. Furthermore, we perform imaging at different temperatures and determine the Curie temperature of the flakes at Tc~300 K. These results provide the basis for realizing a room-temperature monolayer ferromagnet with Fe${}_5$GeTe${}_2$. This work also demonstrates that the imaging technique enables a rapid screening of multiple flakes simultaneously, thereby paving the way towards high throughput characterization of potential 2D magnets near room temperature.

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• Magnetic order in the computational 2D materials database (C2DB) from high throughput spin spiral calculations
• Nitrogen-vacancy magnetometry of CrSBr by diamond membrane transfer
• Thermal cycling induced alteration of the stacking order and spin-flip in the room temperature van der Waals magnet Fe${}_5$GeTe${}_2$
• (Fe${}_{1-x}$Ni${}_x$)${}_5$GeTe${}_2$: an antiferromagnetic triangular Ising lattice with itinerant magnetism
• Imaging current control of magnetization in Fe${}_3$GeTe${}_2$ with a widefield nitrogen-vacancy microscope
• Towards high spatial resolution magnetic imaging with a compact practical quantum diamond microscope
• Tuning magnetic anisotropy in Fe${}_5$GeTe${}_2$ monolayer through doping and strain
• Flat bands and magnetism in $\mathbf{F}{\mathbf{e}}_4\mathbf{GeT}{\mathbf{e}}_2$ and $\mathbf{F}{\mathbf{e}}_5\mathbf{GeT}{\mathbf{e}}_2$ due to bipartite crystal lattices
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• Laser patterning of the room temperature van der Waals ferromagnet 1$T$-CrTe${}_2$
• Quantum Imaging of Ferromagnetic van der Waals Magnetic Domain Structures at Ambient Conditions
• Unprecedented Spin-Lifetime of Itinerant Electrons in Natural Graphite Crystals