Tunneling current-induced butterfly-shaped domains and magnetization switching in DBMTJs

Double barrier magnetic tunnel junctions (DBMTJs) with the layer architecture of Ta (5 nm)/Cu (20 nm)/Ni₇₉Fe₂₁(10 nm)/Ir₂₂Mn₇₈ (12 nm)/Co₇₅Fe₂₅ (4 nm)/Al (0.9 nm)-oxide/Ni₇₉Fe₂₁(3 nm)/Al (0.9 nm)-oxide/Co₇₅Fe₂₅(4 nm)/Ir₂₂Mn₇₈ (12 nm)/Py(10 nm)/Cu(30 nm)/Ta(5 nm) were mircofabricated. At room temperature, TMR ratio of 18.7% and 28.4%, resistance-area products(RS) of around 10.3 and 12.7 kΩμm² and coercivity H_C of 17.5 and 2.0 Oe, were obtained for the DBMTJ at the as-deposited state and the after annealing state respectively. The micromagnetics simulations show that the dynamic butterfly-shaped domains and magnetization switching may occur in the free layer when a tunneling current of the order of 1 to 20 mA passes though the DBMTJ. It decreases the magnetization in the free layer, which may be the one of the reasons of the low TMR ratio observed in the DBMTJ.