Micromagnetic study on write operation in submicron magnetic random access memory cell

In a spin-valve random access memory, the binary bit states of the storage cell are determined by the magnetization direction in the free magnetic layer. The write operation of a submicron memory cell element has been studied by a micromagnetic computation based on an energy minimization scheme, which aids in the chip design. The magnetization of the binary bit states in the element was found to take a single domain structure having the opposite direction of the long-axis component. The mean long-axis component of magnetization of each binary state was ±0.97 without external fields. The selective switching of the bit state in the element was performed by the write currents applied into the two level conductors overlying the element for various conditions. The influence of the write currents to the neighboring element on a two-dimensional memory array with a 1×1 μm pitch was also simulated, in order to confirm the selective switching of the memory element. It was found that the selective write current amplitude decreased with an increasing assist current amplitude and the range was extended by the large difference of the transverse magnetic field between the selected and neighboring element. The effect of the exchange interaction from the pinned magnetic layer on the write operation was also discussed.