In a magnetic random access memory using a static differential signal due to the giant magnetoresistance effect, the write operation is performed by the switching of the magnetization direction in the free magnetic layer. The dynamic properties of the write operation in a sub-micron memory cell has been studied by a micromagnetic computation, which is important in order to estimate the power consumption and the access time in the memory. The magnetization switching process performed by step pulse currents have been investigated and the minimum pulse width required for the switching has been clarified. Both the minimum pulse width and the power consumption decreased with an increasing write current amplitude through the selective write operation range. The bit state switching was found to be caused by the incoherent rotation of the magnetization in the fine thin film pattern due to the demagnetization field. The dependence of the switching process on the damping constant is also discussed.
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