Enhancement of coercive field in atomically-thin quenched Fe5GeTe2

We have fabricated thin films of a van der Waals (vdW) ferromagnetic metal Fe₅GeTe₂ and characterized them by measuring the anomalous Hall effect. While the bulk Fe₅GeTe₂ does not exhibit a perpendicular magnetic anisotropy (PMA) unlike Fe₃GeTe₂, PMA emerges in the thin film devices. Furthermore, the PMA is enhanced with decreasing thickness of Fe₅GeTe₂. In particular, a thin film (5 unit-cell layer) device fabricated with Fe₅GeTe₂ quenched at 1050 K has two times larger coercive field than that prepared without quenching. Such a PMA should be useful for future vdW spintronic devices