Tunneling current-induced butterfly-shaped domains and magnetization switching in double-barrier magnetic tunnel junctions

Double barrier magnetic tunnel junction (DBMTJ) with layer structures Ta/Cu/Ni₇₉Fe₂₁/Ir₂₂Mn₇₈/Co₇₅Fe₂₅/Al -oxide/Ni₇₉Fe₂₁/Al-oxide/Co₇₅Fe₂₅/Ir₂₂Mn₇₈/ Py/Cu/Ta are deposited on Si/SiO₂ wafer using magnetron sputtering. Tunneling magnetoresistance(TMR) ratio of 18.7% and 28.4%, resistance-area product RS of around 12.7 and 10.3 kΩμm² and coercivity of 17.5 and 2.0 Oe at room temperature are obtained for the DBMTJ. Micromagnetic simulations for the dynamic domain structures under increasing DC current and the magnetic switching properties are done using the energy minimization method. The magnetocrystalline anisotropy constant K₁=1.0×10³ erg/cm³, spontaneous magnetization M_s=800 Oe, and exchange interaction constant A=1.0×10^-6 erg/cm values for the free layer are taken from the parameters of Ni₇₉Fe₂₁ alloy. The simulations show that the dynamic butterfly-shaped domains and magnetization switching can occur in the free layer when a DC current passes through the DBMTJ on the order of 100 μA to 10 mA, under a DC bias voltage of 10-1000 mV. It decreases the magnetization in the free layer which results into the low TMR ratio observed in the DBMTJ.