Stochastic macromodel of magnetic tunnel junction resistance variation and critical current dependence on resistance variation for SPICE simulation

Abstract

The resistance distribution of a magnetic tunnel junction (MTJ) shows nonuniformity according to various MTJ parameters. Moreover, this resistance variation leads to write-current density variation, which can cause serious problems when designing peripheral circuits for spin transfer torque magnetoresistance random access memory (STT-MRAM) and commercializing gigabit STT-MRAM. Therefore, a macromodel of MTJ including resistance, tunneling magnetoresistance ratio (TMR), and critical current variations is required for circuit designers to design MRAM peripheral circuits, that can overcome the various effects of the variations, such as write failure and read failure, and realize STT-MRAM. In this study, we investigated a stochastic behavior macromodel of the write current dependence on the MTJ resistance variation. The proposed model can possibly be used to analyze the write current density in relation to the resistance and TMR variations of MTJ with various parameter variations. It can be very helpful for designing STT-MRAM circuits and simulating the operation of STT-MRAM devices considering MTJ variations.

The magnetoresistance acquisition system of a perpendicular magnetic tunnel junction using LabVIEW software

“…The optimal value of 𝐻 𝑏 is obtained from R-H measurements plotted in figure 8(a). The difference in slope (Δslope) for the four curves representing four different pulse width values, when current is swept between 0 μA and 200 μA as shown in figure 8(b) is dependent on the temperature and barrier quality of the MTJ [25]. Since, the four curves are for the same barrier and measured at constant room temperature, Δslope is almost zero.…”