Estimation of thermal durability and intrinsic critical currents of magnetization switching for spin-transfer based magnetic random access memory

To realize a large capacity magnetic random access memory (MRAM) that uses spin-transfer switching for writing, it is essential to evaluate thermal durability and intrinsic critical currents correctly. Here, we examined the theoretically predicted logarithmic relationship between critical currents of spin-transfer switching and duration of injected pulsed currents using giant magnetoresistive (GMR) samples with different magnetic materials, e.g., Co, Co–Fe25, and CoFeB. This relationship was verified for the samples by giving reasonable thermal-durability coefficients and intrinsic critical currents as fitting parameters. We found that thermal durability was underestimated when an effective magnetic field acted on magnetic memory cells antiparallel to their magnetization. We then experimentally demonstrated that thermal assistance in spin-transfer switching decreased with increasing thermal durability.