Write stability of 2.0×20 μm2 M-R memory cells

Write stability tests have been performed on 2×20 μm² magnetoresistive memory cells by performing continuous write operations at a 60 MHz rate for a period of 15 months; each cell was subjected to a total of 2.0×10¹⁵ write operations. Within experimental error, no change in the element write thresholds occurred. As expected, element behavior was similar to that of plated wire or core cells; no wear-out phenomena such as occurs with ferroelectric cells were found. Tests were performed at room temperature, 23±2°C. Annealing tests were conducted at 250°C for 1 h in a 97%N₂3%H₂ environment to experimentally determine annealing effects on element thresholds. The perturbations on the switching thresholds were found to depend on the state of stored information in the bits. The shifts in the threshold curves were consistent with local skewing of the easy axis in the direction of the magnetization