  The discovery of van der Waals (vdW) magnets opened up a new paradigm for
condensed matter physics and spintronic technologies. However, the operations
of active spintronic devices with vdW magnets are so far limited to cryogenic
temperatures, inhibiting its broader practical applications. Here, for the
first time, we demonstrate room temperature spin-valve devices using vdW
itinerant ferromagnet Fe5GeTe2 in heterostructures with graphene. The tunnel
spin polarization of the Fe5GeTe2/graphene vdW interface is detected to be
significantly large ~ 45 % and negative at room temperature. Lateral spin-valve
device design enables electrical control of spin signal and realization of
basic building blocks for device application such as efficient spin injection,
transport, precession, and detection functionalities. Furthermore, measurements
with different magnetic orientations provide unique insights into the magnetic
anisotropy of Fe5GeTe2 and its relation with spin polarization and dynamics in
the heterostructure. These findings open opportunities for the applications of
vdW magnet-based all-2D spintronic devices and integrated spin circuits at
ambient temperatures.
