Effect of an antiferromagnetic order on tailoring Dzyaloshinskii- Moriya interaction in Pt/Co/IrMn trilayer

Antiferromagnet (AFM) has currently participated in the spin-orbit torque (SOT) magnetoresistive random access memory (MRAM) technolopgy due to its great potential to be applied to the field-free SOT switching and promote the thermal stability of MRAM. However, effect of the introduction of AFM into the basic structure of SOT-MRAM composed of a heavy metal/ferromagnet (FM) bilayer was still not comprehensively understood. This work reports the effect of how an antiferromagnetic (AFM) order modifies the strength of Dzyaloshinskii-Moriya interaction (DMI) in a heavy metal (Pt)/FM (Co)/AFM (IrMn) trilayer, studied by SOT switching and loop-shift method. Increasing the AFM order reflected on exchange bias (H
ex
) through increasing the thickness of IrMn appears to significantly reduce the DMI strength of the trilayer, which leads to the reduction of the external field for yielding a complete SOT switching. The reduced DMI strength may ascribe to the Hex-hosted uni-directional anisotropy suppressing the neighboring spin canting in the FM layer. This stabilization for the magnetic moments via the H
ex
-hosted uni-directional anisotropy also improved the stability of SOT switching on the random read/write characterization, in which the strong AFM order would promote the memristivity for neuromorphic application and the weak AFM order would give rise to the stochasticity for the purpose of physically unclonable functionality. This work demonstrates the significance of an intrinsic tuning over the AFM order would serve as a switch to turn the SOT device into a stochastic/memristive cell to bridge probabilistic and neuromorphic computing.