Exchange bias effect in the total two-dimensional van der Waals heterostructures of Fe5-xGeTe2/CrPS4

We construct vertically stacked van der Waals (vdWs) heterostructures using two-dimensional (2D) ferromagnetic (FM) metal Fe5-xGeTe2 (20 nm <= t <= 90 nm) nanoflakes with a strong perpendicular magnetic anisotropy (PMA) and similar to 60 nm thick A-type antiferromagnetic semiconductor CrPS4 nanoflakes via the mechanical exfoliation and transfer method. We investigate the detailed temperature and FM thickness dependences of the coercive field H-C and the exchange bias field H-EB by isothermal anomalous Hall resistance loops with several field cooling processes. Our results indicate that H-C increases monotonically with decreasing FM nanoflake thickness t, consistent with the significant enhancement of PMA with the decrease of t in the single Fe5-xGeTe2 nanoflakes. Additionally, we observe a moderate exchange bias effect below the blocking temperature of 20 K, which is significantly below the N & eacute;el temperature T-N = 38 K of the bulk CrPS4. Unlike H-C, H-EB shows a saturation or drop tendency as the thickness t is less than 35 nm. Our findings highlight the feasibility of achieving an apparent interfacial magnetic coupling in 2D magnetic vdWs heterostructures via a mechanical exfoliation and transfer approach, which may facilitate the applications of 2D magnetic vdWs in spintronics.