Noise properties of magnetic tunnel junctions

Magnetron sputtering was used to prepare the magnetic tunnel junction (MTJ) with the stacking structure SiO₂/Ta(3 nm)/Ni₈₀Fe₂₀(3 nm)/Cu(20 nm)/Ni₈₀Fe₂₀(3 nm)/IrMn(10 nm)/Co₇₅Fe₂₅(5 nm)/Al(0.8 nm)-oxide/Co₇₅Fe₂₅(5 nm)/Ni₈₀Fe₂₀(20 nm)/Ta(5 nm). Low frequency magnetic noise was measured on MTJ at critical annealing temperature at which the MR ratio increases at 250 °C and decreases at 350 °C due to interlayer diffusion of Mn. The noise increases at the transition indicating that it was magnetic in origin and therefore is field dependent at the corresponding annealing temperatures.