Magnetic immunity of spin-transfer-torque MRAM

Spin-transfer-torque magnetic random-access memory (STT-MRAM) devices are projected to find their applications in a wide range of systems such as portable devices which may be influenced by external magnetic fields. Therefore, it is important to study the magnetic immunity for the development of STT-MRAM immune to the data loss due to accidental or deliberate exposure to high magnetic fields. In this work, we propose a method to analyze the magnetic immunity of STT-MRAM arrays based on the bit error rate (BER) data in the presence of an external magnetic field. We propose an analytical equation to express the standard deviation of the energy barrier for the STT-MRAM array using a domain wall assisted switching model, which is confirmed using Monte Carlo simulations. We study 40 Mb BER data and predict that the STT-MRAM array can sustain a maximum field of 690 Oe and maintain BER below 0.1 ppm for ten-year exposure to the DC magnetic field at 85 °C.