Field-free manipulation of exchange bias in perpendicularly magnetized Pt/Co/IrMn structures by spin-orbit torque

Electrical manipulation of exchange bias by spin-orbit torque (SOT) is promising for the design of spintronic devices, such as multilevel memory and neuromorphic computing. However, an external magnetic field is required to assist manipulation of exchange bias, which poses a challenge for applications. In this work, we propose a promising approach to the field-free manipulation of exchange bias through an in-plane ferromagnetic layer deposited on the current line of the Hall bar device, which can generate an internal effective in-plane field to realize field-free SOT switching. Furthermore, our devices present memristive behaviors in the absence of an external field, offering the practical potential for the construction of artificial synapses based on exchange-biased systems. Meanwhile, this method can ensure the high SOT efficiency and a thermal stability factor ($\mathrm{\ensuremath{\Delta}}$) of around 56, indicating over 10 years of data retention. The approach to field-free manipulation of exchange bias by SOT is promising for applications and the development of spintronic devices.