Observation of Intermediate States in Magnetic Tunnel Junctions With Composite Free Layer

The current-induced magnetization switching was studied in the MTJ devices with composite free layer (CoFeB/CoFeB-oxide/CoFeB). The stable intermediate state was observed due to the multi-domain structure induced by the dipole field and large device size. Two different stable intermediate states were observed in different applied current direction. The switching mechanisms of those two intermediate states are different, which is also indicated by the switching current distribution. Reversible intermediate state was also observed at low applied current, which may be due to the domain nucleation.