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Mesoscale Magnetostructural Phase Separation in Fe-deficient Fe5GeTe2.
Haoyang Ni1,2, Eric R Hoglund2, Jordan A Hachtel2
1Department of Materials Science and Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois, 61801, USA.
Advanced Materials (Deerfield Beach, Fla.)
|December 26, 2025
Summary
Controlling magnetism in 2D ferromagnets like iron germanium telluride (Fe5GeTe2) depends on secondary phase inclusions. Mesoscale inclusions create in-plane anisotropy, while nanoscale ones preserve out-of-plane anisotropy.
Area of Science:
- Materials Science
- Condensed Matter Physics
- Nanotechnology
Background:
- 2D Van der Waals ferromagnets are key for spintronics.
- Iron-germanium-telluride (Fe5GeTe2) shows promise due to its high Curie temperature and layered structure.
- Controlling magnetic anisotropy in Fe5GeTe2 is crucial but poorly understood.
Purpose of the Study:
- Investigate the origin of sample-dependent magnetic anisotropy in Fe5GeTe2.
- Establish the relationship between material structure and magnetic properties.
- Develop a framework for tuning magnetism in 2D materials.
Main Methods:
- Spatially resolved cryogenic scanning transmission electron microscopy (STEM).
- Correlative mapping of magnetism, lattice structure, and chemistry.
- Analysis across atomic-to-micron length scales.
Main Results:
- Mesoscale inclusions of a Fe-deficient secondary phase significantly alter magnetic behavior.
- Nanoscale inclusions have minimal impact on magnetic anisotropy.
- Quenching induces phase separation leading to in-plane anisotropy.
- Slow cooling preserves out-of-plane anisotropy by limiting phase separation.
Conclusions:
- A critical mesoscale length governs magnetic anisotropy in Fe5GeTe2.
- Thermal processing (cooling rate) dictates phase separation and resulting magnetic behavior.
- Provides a predictive framework for tuning magnetic anisotropy in 2D materials.
Keywords:
2D ferromagnets4D scanning transmission electron microscopyFe5GeTe2Lorentz 4D‐STEMcryogenic STEMMore Related Videos
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