  The exceptional properties of two-dimensional (2D) magnet materials present a
novel approach to fabricate functional magnetic tunnel junctions (MTJ) by
constructing full van der Waals (vdW) heterostructures with atomically sharp
and clean interfaces. The exploration of vdW MTJ devices with high working
temperature and adjustable functionalities holds great potential for advancing
the application of 2D materials in magnetic sensing and data storage. Here, we
report the observation of highly tunable room-temperature tunneling
magnetoresistance through electronic means in a full vdW Fe3GaTe2/WSe2/Fe3GaTe2
MTJ. The spin valve effect of the MTJ can be detected even with the current
below 1 nA, both at low and room temperatures, yielding a tunneling
magnetoresistance (TMR) of 340% at 2 K and 50% at 300 K, respectively.
Importantly, the magnitude and sign of TMR can be modulated by a DC bias
current, even at room temperature, a capability that was previously unrealized
in full vdW MTJs. This tunable TMR arises from the contribution of
energy-dependent localized spin states in the metallic ferromagnet Fe3GaTe2
during tunnel transport when a finite electrical bias is applied. Our work
offers a new perspective for designing and exploring room-temperature tunable
spintronic devices based on vdW magnet heterostructures.
