  Antiferromagnetic (AFM) van der Waals (vdW) materials provide a novel
platform for synthetic AFM spintronics, in which the spin-related
functionalities are derived from manipulating spin configurations between the
layers. Metallic vdW antiferromagnets are expected to have several advantages
over the widely-studied insulating counterparts in switching and detecting the
spin states through electrical currents but have been much less explored due to
the lack of suitable materials. Here, utilizing the extreme sensitivity of the
vdW interlayer magnetism to material composition, we report the itinerant
antiferromagnetism in Co-doped Fe4GeTe2 with TN ~ 210 K, an order of magnitude
increased as compared to other known AFM vdW metals. The resulting spin
configurations and orientations are sensitively controlled by doping, magnetic
field, temperature, and thickness, which are effectively read out by electrical
conduction. These findings manifest strong merits of metallic vdW magnets with
tunable interlayer exchange interaction and magnetic anisotropy, suitable for
AFM spintronic applications.
