Switching time and current reduction using a composite free layer in magnetic tunnel junctions

The theoretical predictions [1] and the experiments [2] of spin transfer switching demonstrated that the spin transfer torque random access memory (STTRAM) is one of the promising candidates for future universal memory. The basic element of the STTRAM is a magnetic tunnel junction (MTJ), a sandwich of two magnetic layers separated by a thin non-magnetic spacer (Fig.1a). The reduction of the current density required for switching and the increase of the switching speed are the most important challenges in STTRAM research [3]. It has been demonstrated [4] that the critical current density is decreased in a penta-layer magnetic tunnel junction as shown in Fig.1b.