Micro magnetic simulation of write error probability in STT-MRAM

STT MRAM is one of the most promising candidates for the next generation non-volatile memory. The STT-MRAM write operation is to switch the magnetization direction of ferromagnetic free layer with spin transfer torque by current injection. A ferromagnetic thin film used in it is so small volume that the thermal fluctuation due to ambient temperature has to be considered in the device design. Its process is described by a stochastic probability distribution. In this paper, a write error probability function in STT MRAM at finite temperature is investigated based on the result of LLG micro magnetic simulation. The function is found to be a Weibull type function with modulus, beta. The physical meanings of beta is found to be an index of competitions between thermal activation process and spin transfer torque ones in switching of STT MRAM at finite temperature.