Abstract
There is accelerating interest in developing memory devices using antiferromagnetic (AFM) materials, motivated by the possibility for electrically controlling AFM order via spin-orbit torques, and its read-out via magnetoresistive effects. Recent studies have shown, however, that high current densities create non-magnetic contributions to resistive switching signals in AFM/heavy metal (AFM/HM) bilayers, complicating their interpretation. Here we introduce an experimental protocol to unambiguously distinguish current-induced magnetic and nonmagnetic switching signals in AFM/HM structures, and demonstrate it in IrMn3/Pt devices. A six-terminal double-cross device is constructed, with an IrMn3 pillar placed on one cross. The differential voltage is measured between the two crosses with and without IrMn3 after each switching attempt. For a wide range of current densities, reversible switching is observed only when write currents pass through the cross with the IrMn3 pillar, eliminating any possibility of non-magnetic switching artifacts. Micromagnetic simulations support our findings, indicating a complex domain-mediated switching process.
Highlights
There is accelerating interest in developing memory devices using antiferromagnetic (AFM) materials, motivated by the possibility for electrically controlling Antiferromagnetic materials (AFMs) order via spin-orbit torques, and its read-out via magnetoresistive effects
The first requirement was initially demonstrated in antiferromagnetic films with broken inversion symmetry (CuMnAs8,19–21, Mn2Au22–26), where a damping-like Néel spin–orbit torque (SOT) was generated due to the current flowing in the bulk of the material, resulting in the motion of AFM domains
It is noteworthy that a similar square-shaped switching signature was observed due to AFM order manipulation in the PtMn/Pt and PtMn/Ta systems[37]. Both for device applications and fundamental studies of AFM switching, it remains a challenge to reliably and directly separate the nonmagnetic and magnetic contributions to resistive switching signals in AFM/heavy metal (AFM/heavy metal (HM)) structures. This is difficult for AFM/HM devices because, unlike FM/HM structures, magnetoresistance effects are typically smaller in AFMs, switching current densities are higher, and there is typically no possibility to manipulate the magnetic order with magnetic fields, something which can be routinely done with modest magnetic fields for FM/HM samples
Summary
There is accelerating interest in developing memory devices using antiferromagnetic (AFM) materials, motivated by the possibility for electrically controlling AFM order via spin-orbit torques, and its read-out via magnetoresistive effects. Several recent reports have indicated that some of the electrically measured switching signals in such test structures may have non-magnetic origins due to thermal effects and atomic motion (e.g., electromigration) in the HM layer, in cases where the applied current densities were high[40,41,42].
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