We propose a profile of write pulse current-density to switch magnetization in a perpendicular magnetic tunnel junction to reduce switching time and write energy as well. Our simulated results show that an overshoot transient pulse current-density (current spike) imposed to conventional rectangular-shaped pulse current-density (main pulse) significantly improves switching speed that yields the reduction in write energy accordingly. For example, we could dramatically reduce the switching time by 80% and thereby reduce the write energy over 9% in comparison to the switching without current spike. The current spike affects the spin dynamics of the free layer and reduces the switching time mainly due to spin torque induced. On the other hand, the large Oersted field induced causes changes in spin texture. We believe our proposed write scheme can make a breakthrough in magnetic random access memory technology seeking both high speed operation and low energy consumption.
Although promising as a future memory solution, the spin-torque transfer magnetic RAM has critical drawbacks due to small operation margin in low supply voltage and large area of sensing circuit. To overcome these disadvantages, we propose a novel sensing circuit that utilizes the data-dependent body-bias scheme with a single reference cell. Through Monte Carlo simulations using 45-nm process technology model parameters, the proposed circuit is verified to be highly robust to the variations in threshold voltage and cell resistance at ultra-low supply voltages without sensing speed degradation. The proposed circuit has a read access pass yield of 96.5% for 16Mb memory at VDD = 0.7 V when the standard deviation of cell resistance is 10 %. In addition, the area overhead is also reduced by 79% compared to the conventional sensing circuit.
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