Kink-free design of submicrometer MRAM cell

Full micromagnetic simulations have been performed to investigate the origin of a kink in a magnetoresistive curve and to design a kink-free magnetoresistive random access memory (MRAM) cell. The kink in an at-field curve can originate from the 2π-wall or the vortex formation, which is strongly dependent on the magnetic properties and the geometry of a free layer. The kink originating from the 2π-wall formation was found to disappear in a remanent magnetization curve; therefore, it should not affect the selectivity of a MRAM array. It turned out that the vortex formation was the major origin of the kink when the free layer has the high saturation magnetization and the thick layer thickness. This vortex state is a local minimum state even after removing the external field. Finally, we found kink-free criteria for various saturation magnetizations, thicknesses, and aspect ratios of a free layer.