Reduction of shunt current in buffer-free IrMn based spin-valve structures

Highlights: • IrMn thickness and the lack of buffer layer play a critical role in shunt current. • Both H_EB and T_B values are significantly enhanced with post-annealing of IrMn. • Buffer-free spin valves with 6 nm IrMn exhibit exchange bias high above room temperature. The presence of thick buffer layers in magnetic sensor devices decreases sensor sensitivity due to shunt currents. With this motivation, we produced IrMn-based spin-valve multilayers without using buffer layer. We also studied the effects of post-annealing and IrMn thickness on exchange bias field (H_EB) and blocking temperature (T_B) of the system. Magnetization measurements indicate that both H_EB and T_B values are significantly enhanced with post-annealing of IrMn layer. In addition, we report that IrMn thickness of the system strongly influences the magnetization and transport characteristics of the spin-valve structures. We found that the minimum thickness of IrMn layer is 6 nm in order to achieve the lowest shunt current and high blocking temperature (>300 K). We also investigated the training of exchange bias to check the long-term durability of IrMn-based spin-valve structures for device applications.