Effect of Geometrical Modulation on pMTJ Magnetization Reversal

Spin-transfer torque-magnetic random access memory (STT-MRAM) is one of the most prominent spintronic devices for replacing conventional electronic memory devices due to its extraordinary performance as it delivers fast operational speed, non-volatility, and a high-memory density. At advanced technology nodes, manufacturing process would invariably lead to bit on bit variation of STT-MRAM cell at wafer level. Here, we show that in a perpendicularly magnetized magnetic tunnel junction (MTJ), the in-plane demagnetizing tensor greatly influences the magnetization switching process of the free layer (FL). The geometrical asymmetricity was introduced to induce a varying in-plane demagnetizing field. This impacts the stability of the MTJ and requires a larger anisotropy to sustain an out-of-plane magnetization state. Interestingly, a faster switching of the FL comprising the MTJ is observed. This resultant rapid switching is ascribed to the nucleation of a reversal embryo at the defect.