MULTI-STATE MRAM WITH IMPROVED STORAGE DENSITY

摘要

A multi-state magnetoresistive random access memory device (7) comprising a pinned ferromagnetic region (19) having a magnetic moment vector (20) fixed in a preferred direction in the absence of an applied magnetic field, an non-ferromagnetic spacer layer (24) positioned on the pinned ferromagnetic region, and a free ferromagnetic region (26) with an anisotropy designed to provide a free magnetic moment vector (30) within the free ferromagnetic region with N stable positions, wherein N is a whole number greater than two, positioned on the non-ferromagnetic spacer layer. The number N of stable positions can be induced by a shape anisotropy of the free ferromagnetic region wherein each N stable position has a unique resistance value.