  We investigate the impact of monoatomic vacancies in 2D materials on the
performance of magnetic tunnel junction (MTJ) devices using first-principles
calculations within Density Functional Theory (DFT). Specifically, we analyze
the influence on hexagonal boron nitride (hBN) with various layer
configurations, uncovering distinct transmission probability patterns.
Transmission calculations were conducted using the Landauer-B\"uttiker formula
employing the Non-Equilibrium Green's Function (NEGF) method. In the
Ni/hBN(V$_B$)-hBN/Ni system, a significant reduction in transmission
probability was observed compared to non-vacancy configurations. However, when
two hBN vacancies were considered, creating the Ni/hBN(V$_B$)-hBN(V$_B$)/Ni MTJ
system, a new transmission channel mediated by vacancy localized states
emerged. The introduction of a monoatomic boron vacancy in the middle hBN layer
of the Ni/3hBN/Ni system revealed nuanced effects on the transmission
probability, highlighting alterations in the spin minority and majority
channels. Additionally, we explore the monoatomic vacancy in the graphene layer
in the Ni/hBN-Gr-hBN/Ni MTJ, uncovering a unique transmission channel
influenced by the proximity effect. Our findings suggest that the creation of
monoatomic vacancies on the insulator barrier of 2D materials induces
distinctive characteristics shaped by the interaction between the surface state
of the electrode and the localized state of the monoatomic vacancy layer in the
MTJ system.
