Multibit Cells Schemes for Toggle MRAM Applications

A new multibit magnetic random access memory (MRAM) cell of toggle switching type is presented. The multibit stack consists of multiple conventional toggle MRAM cells connected in series. These cells are identical except that their cell geometry, anisotropy, and pinned directions are oriented differently from each other. The selective write of the individual cell is achieved by using three phases of word and bit line current generating a contiguous magnetic field rotating past the easy axis of the targeted cell. Two-, four-, and six-bit toggle cell configurations are found to be feasible. This approach has the potential to greatly enhance the density of the MRAM cell for a given lithography ground rule