  Van der Waals (vdW) magnets are promising owing to their tunable magnetic
properties with doping or alloy composition, where the strength of magnetic
interactions, their symmetry, and magnetic anisotropy can be tuned according to
the desired application. However, most of the vdW magnet based spintronic
devices are so far limited to cryogenic temperatures with magnetic anisotropies
favouring out-of-plane or canted orientation of the magnetization. Here, we
report room-temperature lateral spin-valve devices with strong in-plane
magnetic anisotropy of the vdW ferromagnet (Co0.15Fe0.85)5GeTe2 (CFGT) in
heterostructures with graphene. Magnetization measurements reveal above
room-temperature ferromagnetism in CFGT with a strong in-plane magnetic
anisotropy. Density functional theory calculations show that the magnitude of
the anisotropy depends on the Co concentration and is caused by the
substitution of Co in the outermost Fe layer. Heterostructures consisting of
CFGT nanolayers and graphene were used to experimentally realize basic building
blocks for spin valve devices such as efficient spin injection and detection.
The spin transport and Hanle spin precession measurements prove a strong
in-plane and negative spin polarization at the interface with graphene, which
is supported by the calculated spin-polarized density of states of CFGT. The
in-plane magnetization of CFGT at room temperature proves its usefulness in
graphene lateral spin-valve devices, thus opening further opportunities for
spintronic technologies.
