Near-room temperature ferromagnetism and a tunable anomalous Hall effect in atomically thin Fe₄CoGeTe₂

Area of Science:

• Condensed Matter Physics
• Materials Science
• Nanotechnology

Background:

• Itinerant ferromagnetism is crucial for spintronics, enabling spin transport and manipulation.
• Achieving room-temperature ferromagnetism in ultrathin materials remains a significant challenge.

Purpose of the Study:

• To realize and investigate near-room temperature itinerant ferromagnetism in cobalt-doped Fe5GeTe2 thin flakes.
• To explore the thickness-dependent magnetic and transport properties of these materials.
• To understand the underlying mechanisms of ferromagnetism and the anomalous Hall effect in two-dimensional van der Waals magnets.

Main Methods:

• Fabrication of cobalt-doped Fe5GeTe2 thin flakes.
• Experimental characterization of magnetic properties, including ferromagnetic transition temperature (TC).
• Theoretical calculations to predict ferromagnetism in monolayer structures.
• Measurement of the anomalous Hall effect as a function of temperature and thickness.

Main Results:

• Near-room temperature itinerant ferromagnetism observed in Co-doped Fe5GeTe2, with TC around 323-337 K for thicknesses down to 12 nm.
• Ferromagnetism persists down to 2 nm (bilayer), with TC around 284 K, and is predicted to exist in monolayer Fe4CoGeTe2.
• An unusual temperature- and thickness-dependent intrinsic anomalous Hall effect was observed.
• The anomalous Hall effect is attributed to thickness-dependent band structure modifications affecting Berry curvature near the Fermi level.

Conclusions:

• Atomically thin Fe5GeTe2 exhibits robust near-room temperature ferromagnetism and a tunable anomalous Hall effect.
• These findings provide insights into the exotic transport properties of 2D van der Waals magnetic materials.
• The material holds promise for future applications in spintronics and low-dimensional magnetic devices.