Barrier-dependent positive-to-negative tunneling magnetoresistance in MnBi2Te4-based magnetic tunnel junctions

As an indispensable component in magnetic tunnel junctions (MTJs) design, the selection and design of barrier materials have attracted extensive research attention. In this study, we construct a Cu/MnBi2Te4/MoSi2N4/MnBi2Te4/Cu MTJ and systematically investigate its spin-dependent electronic transport properties using non-equilibrium Green's function formalism combined with density functional theory. Interestingly, the tunneling magnetoresistance (TMR) undergoes a sign reversal from positive to negative with increasing bias voltage, reaching a remarkable negative TMR of -264%, which sets a new record for MnBi2Te4-based MTJs where values beyond -100% had never been reported. Through analysis of the transmission spectra, projected local density of states and comparison with a bilayer h-BN barrier, this unique transport property is attributed to bias-induced barrier tilting, which alters the transmission weights of spin-polarized channels. These findings not only provide insights into resolving read-write path conflicts in MRAMs but also offer guidance for possible experimental exploration of MoSi2N4-based MTJs.