Temperature dependence of exchange coupling in Mn₇₅Ir ₂₅/Co₇₀Fe₃₀/AlO_x/Co ₇₀Fe₃₀/Ni₈₀Fe₂₀ MTJs

Magnetic Tunnel Junctions (MTJs) were fabricated on thermally oxidized Si(100) wafers by utilizing DC magnetron sputtering. Magnetic properties of MTJs with structure of Ta(50)/Cu(100)/Ta(50)/Ni₈₀Fe₂₀(20)/ Cu(50)/Mn₇₅Ir₂₅(100)/Co₇₀Fe₃₀(25)/ AlO_x(15)/Co₇₀Fe₃₀(25)/Ni₈₀Fe ₂₀(t)/Ta(50), where t = 0, 100 and 100 Å, were investigated by using SQUID, XRD and MR analyzer. Exchange bias field is inversely proportional to temperature for t = 0 Å sample. XRD shows the improvement of (111) texture of IrMn₃ and Cu after annealing. The exchange bias field decreases with increasing temperature due to thermal effect. And it is the highest for t = 100 Å due to increased crystallites size of IrMn ₃. For the free layer, the temperature dependence of interlayer exchange coupling involves the same mechanism as that of exchange bias.