Characterization and modeling of perpendicular spin transfer torque

My Master Thesis project consisted in the electrical characterization and physical modeling of perpendicular spin-transfer torque magnetoresistive memory (p-STT-MRAM), an emerging non volatile memory (NVM) considered a promising candidate for next-generation memory due to fast switching and current scalability. The electrical transport and switching properties of the devices were investigated in both DC and AC-pulsed regimes and a simple compact model for their reproduction was devised; in addition a Monte Carlo extension is able to account for the cycle-to-cycle variability of the switching parameters. Moreover, even though cycling endurance is of paramount importance for memory applications, its characterization methodology and physical modeling are not yet well established. This work presents a method for the evaluation of STT-MRAM endurance and a new semi-empirical model of dielectric breakdown in thin MgO tunnel barrier able to account for the dependences on applied voltage, polarity, pulse-width and pulse time delay. The model was used to estimate the applicability of the tested devices in a DRAM-like memory.