## 1 Introduction  
Radiation effects on semiconductor electronic devices have been one of the main concerns of the microelectronic industry, not only for space applications, but also for consumer electronics [1; 2; 3; 4]. Regarding the reliability of electronic products, radiation causes critical damage which threatens the normal operation of integrated circuits based on complementary metal-oxide semiconductor (CMOS) technology. With the shrinking of CMOS fabrication nodes, critical charge and transistor threshold voltages are reduced, and radiation effects become more critical even at a very low level. To describe radiation effects, two types of models are generally used, namely total ionizing dose (TID) and single-event effects (SEEs) as a result of particles colliding with electronic devices [5; 6]. When particles and high-energy rays are injected into semiconductor materials, electron/hole pairs are created after the interaction. The electrons and holes induced by radiation are further recombined, transported, or trapped under electric fields. When the radiant energy accumulates to a certain value, it will damage the electrical performance of CMOS transistors and even lead to permanent failure. The impact of TID on CMOS-based circuits is mainly manifested in two aspects. On one hand, the threshold voltage of the CMOS transistor shifts, which will change the opening degree of the CMOS transistor and cause a shift in the corresponding circuit parameters; on the other hand, it causes an increase in the leakage current, resulting in an increase in circuit power consumption and a shift in the operating point. Both of these aspects may greatly reduce the performance of the CMOS system and even result in complete failure. Due to scaling of CMOS technology, the effects of TID on gate threshold voltage can be negligible in CMOS technologies when the gate oxide thickness is less than 4 nm. When radiation particles with high energy pass through the sensitive area of a CMOS device, the material will ionize electron/hole pairs, and these charges will be transported and collected, resulting in a transient current, which may change the working state of the circuit and even cause irreversible damage to the device. With the rapid scaling down of CMOS technology, SEEs have recently become a substantial threat for the reliability of advanced CMOS technologies, as they result in integrated circuit logic function errors. In fact, single-event upsets (SEUs) have become the largest contributor to CMOS system soft error rates as the amount of charge, which represents stored information, has dropped lower and lower. SEUs mainly occur in memory devices and logic circuits, which may cause \"soft\" errors in flip-flops, memory cells, and digital circuits. SEUs are therefore a significant concern not only for electronics operating in outer space, but also for digital systems that must work reliably. One emerging nonvolatile memory technology, spin-transfer torque magnetic randomness memory (STT-MRAM), becomes an ideal candidate for next-generation memory given its characteristics of non-volatility, high writing speed, and near-infinite endurance. Currently, perpendicular-anisotropy magnetic tunnel junctions (MTJs) are preferred for STT-MRAM due to their adequate storage retention and good scalability. In addition, the storage element of STT-MRAM has been experimentally proved to be highly tolerant to radiation effects [4; 7; 8; 9]. Since it utilizes the electron spin degree of freedom to store digital data instead of electron charges, the nanoscale MTJ is considered to be radiation-hardened, which makes it attractive for applications in space technology. [PERSON] et al. [10] demonstrated that the electrical and the magnetic properties of MgO-based MTJs were not affected by gamma radiation and epithermal neutrons. [PERSON] et al.