  The field of 2D magnetic materials has paved the way for the development of
spintronics and nanodevices with new functionalities. Utilizing
antiferromagnetic materials, in addition to layered van der Waals (vdW)
ferromagnetic materials, has garnered significant interest. In this work, we
present a theoretical investigation of the behavior of MnBi$_2$Te$_4$ devices
based on the non-equilibrium Green's function method. Our results show that the
current-voltage (I-V) characteristics can be influenced significantly by
controlling the length of the device and bias voltage and thus allow us to
manipulate the tunneling magneto-resistance (TMR) with an external bias
voltage. This can be further influenced by the presence of the boron nitride
layer which shows significantly enhanced TMR by selectively suppressing
specific spin channels for different magnetic configurations. By exploiting
this mechanism, the observed TMR value reaches up to 3690\%, which can be
attributed to the spin-polarized transmission channel and the projected local
density of states. Our findings on the influence of structural and magnetic
configurations on the spin-polarized transport properties and TMR ratios give
the potential implementation of antiferromagnetic vdW layered materials in
ultrathin spintronics.
