  Impact of spin transfer torque (STT) on the write error rate of a
voltage-torque-based magnetoresistive random access memory is theoretically
analyzed by using the macrospin model. During the voltage pulse the STT assists
or suppresses the precessional motion of the magnetization depending on the
initial magnetization direction. The characteristic value of the current
density is derived by balancing the STT and the external-field torque, which is
about 5$\times$ 10$^{11}$ A/m$^{2}$. The results show that the write error rate
is insensitive to the STT below the current density of $10^{10}$ A/m$^{2}$.
