Flux-closed MRAM with ultra-low switching current

The VMRAM and pseudo spin-valve MRAM with flux-closed structure are presented to increase the density and to reduce the switching field. The cell includes soft magnetic layer to concentrate the flux, and a conductive layer. From an R-I curve, 8 mA current is required to switch a single layer cell. However, only 1 mA current is required to switch the cell with size of 200 nm for the flux-closed structure. In general, the switching current increases as the cell size increases because of the writing line width increment. However, as the cell size further reduces, the shape anisotropy field caused by the static field increases significantly, thus, the switching current density increases significantly, and the switching current increases even if the writing line width reduces. For a serial of cells with size from 0.1 μm to 0.8 μm, large external field is required to switch the cell due to the two flux-closed magnetic layers.