  Two dimensional (2D) van der Waals (vdW) materials have demonstrated
fascinating optical, electrical and thickness-dependent characteristics. These
have been explored by numerous authors but reports on magnetic properties and
spintronic applications of 2D vdW materials are scarce by comparison. By
performing anomalous Hall effect transport measurements, we have characterised
the thickness dependent magnetic properties of single crystalline vdW Fe3GeTe2.
The nanoflakes of this vdW metallic material exhibit a single hard magnetic
phase with a near square-shaped magnetic loop, large coercivity (up to 550 mT
at 2 K), a Curie temperature near 200 K and strong perpendicular magnetic
anisotropy. Using criticality analysis, we confirmed the existence of magnetic
coupling between vdW atomic layers and obtained an estimated coupling length of
~ 5 vdW layers in Fe3GeTe2. Furthermore, the hard magnetic behaviour of
Fe3GeTe2 can be well described by a proposed model. The magnetic properties of
Fe3GeTe2 highlight its potential for integration into vdW magnetic
heterostructures, paving the way for spintronic research and applications based
on these devices.
