Enhancement of coercive field in atomically-thin quenched Fe 5 GeTe 2

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.