Development of exchange bias in IrMn₃ based tunnel junctions

IrMn based MTJs prepared under a low magnetic field of 30 Oe show pseudospin valve type behavior in the magnetoresistance and magnetization studies with no interlayer coupling or exchnage bias in the as-deposited state, The high field TMR curve shows a coercivity above 500 Oe with a wide distribution in switching fields with a low TMR value of 4%. The low field TMR curve shows sharp switching for the free layer without any interlayer coupling. However, after field annealing at 250°C in a magnetic field of 1 kOe, MTJs show large MR values up to 35% with substantial bias around 1000 Oe for the pinned layer. It also shows an interlayer coupling of 3 Oe for the free layer. The loops corresponding to both the free and pinned layer show sharper switching behavior after annealing. During deposition in presence of the small magnetic field of 30 Oe, possibly, the spin ordering at the AFM/FM interface could not be attained due to the large anisotropy as indicated by the large coercivity for the pinned layer in the as-deposited state. Our results for the field annealed samples show that we can get good magnetoresistive properties in our MTJs after field annealing and cooilng despite no bias state in the as deposited MTJs.