  The magnetic tunnel junctions (MTJ) based on van der Waals (vdW) materials
possess atomically smooth interfaces with minimal element intermixing. This
characteristic ensures that spin polarization is well maintained during
transport, leading to the emergence of richer magnetoresistance behaviors.
Here, using all 2D vdW MTJs based on magnetic metal Fe3GeTe2 and non-magnetic
semiconductor MoSe2, we demonstrate that the magnitude and even sign of the
magnetoresistance can be tuned by the applied voltage. The sign inversion of
the magnetoresistance is observed in a wide temperature range below the Curie
temperature. This tunable magnetoresistance sign may be attributed to the spin
polarizations of the tunneling carriers and the band structure of the two
ferromagnetic electrodes. Such robust electrical tunability of
magnetoresistance extends the functionalities of low-dimensional spintronics
and makes it more appealing for next-generation spintronics with all-vdW MTJs.
