Magnetic memory with tunnel junction memory cells and phase transition material for controlling current to the cells

摘要

A magnetic random access memory (MRAM) array includes a plurality of magnetic tunnel junction (MTJ) memory cells and a plurality of non-electronic switching elements, each MTJ memory cell and an associated switching element being in electrical series connection and located between the bit and word lines of the array. The switching element is a layer of vanadium dioxide, a material that exhibits a first order phase transition at a transition temperature of approximately 65° C. from a low-temperature monoclinic (semiconducting) to a high-temperature tetragonal (metallic) crystalline structure. This phase transition is accompanied by a change in electrical resistance from high resistance at room temperature to low resistance above the transition temperature. To read a memory cell, the vanadium dioxide switching element associated with that cell is heated to lower the resistance of the switching element to allow sense current to pass through the cell, thereby enabling the memory state of the cell to be read.