  Magnetic tunnel junction (MTJ) based on van der Waals (vdW) magnetic layers
has been found to present excellent tunneling magnetoresistance (TMR) property,
which has great potential applications in field sensing, non-volatile magnetic
random access memories, and spin logics. Although MTJs composed of multilayer
vdW magnetic homojunction have been extensively investigated, the ones composed
of vdW magnetic heterojunction is still to be explored. Here we use
first-principles approaches to reveal that the magnetic heterojunction MTJs
have much more distinguishable TMR values than the homojunction ones. In the
MTJ composed of bilayer CrI3/bilayer Cr2Ge2Te6 heterojunction, we find there
are eight stable magnetic states, leading to six distinguishable electronic
resistances. As a result, five sizable TMRs larger than 300% can be obtained
(the maximum TMR is up to 620,000%). Six distinguishable memories are obtained
which is two times larger than that of a four-layered homojunction MTJ. The
underlying relationships among magnetic state, spin-polarized band structures,
and transmission spectrums are further revealed to explain the multiple TMR
values. We also find that the magnetic states and thus TMRs can be efficiently
modulated by an external electric field. This study opens an avenue to the
design of high-performance MTJ devices based on vdW heterojunctions.
