The Heat in Antiferromagnetic Switching

Abstract

Much theoretical and experimental attention has been focused on the electrical switching of the antiferromagnetic (AFM) Néel vector via spin-orbit torque. Measurements employing multiterminal patterned structures of Pt=AFM show recurring signals of the supposedly planar Hall effect and magnetoresistance, implying AFM switching. We show in this Letter that similar signals have been observed in structures with and without the AFM layer, and of an even larger magnitude using different metals and substrates. These may not be the conclusive evidence of spin-orbit torque switching of AFM, but the thermal artifacts of patterned metal structure on substrate. Large current densities in the metallic devices, beyond the Ohmic regime, can generate unintended anisotropic thermal gradients and voltages. AFM switching requires unequivocal detection of the AFM Néel vector before and after SOT switching.

Current-driven writing process in antiferromagnetic Mn2Au for memory applications

“…Correspondingly, within the first generation of experiments on both known compounds with the required structure and AFM ordering, CuMnAs and Mn 2 Au, current pulse induced reversible resistance modifications were reported as evidence for NSOT driven Néel vector rotation [8][9][10][11][12][13] . However, it later became clear that alternative mechanisms such as current pulse induced heat effects 14,15 , electromigration 16 , and rapid quenching induced structural and magnetic modifications 17 can result in resistance modifications similar to the ones reported as well. Additionally, external strain supported Néel vector manipulation in Mn 2 Au was demonstrated 18,19 .…”

Current-driven writing process in antiferromagnetic Mn2Au for memory applications

“…Correspondingly, within the first generation of experiments on both known compounds with the required structure and AFM ordering, CuMnAs and Mn 2 Au, current pulse induced reversible resistance modifications were reported as evidence for NSOT driven Néel vector rotation [8][9][10][11][12][13]. However, it later became clear that alternative mechanisms such as current pulse induced heat effects [14,15], electromigration [16], and rapid quenching induced structural and magnetic modifications [17] can result in resistance modifications similar to the ones reported as well. Thus, microscopic investigations showing the intended current driven alignment of the staggered magnetization directly are essential.…”

Highly Tunable Magnetic and Magnetotransport Properties of Exchange Coupled Ferromagnet/Antiferromagnet-Based Heterostructures

“…Electrical manipulation of the AFM Néel vector with the prospect of encoding information was achieved in various AFM compounds, such as CuMnAs, Mn 2 Au, Mn 3 Pt, , Mn 3 Sn, IrMn 3 , NiO, and CoO, via a relativistic mechanism, namely, Néel order spin–orbit torque (SOT)likely without invoking heat or magnetic fields. In strong contrast, recent experiments showed that significant amounts of charge current densities (≥4 × 10 7 A/cm 2 ) beyond the linear ohmic regime of the devices are needed to switch the Néel vector (or the local AFM domains). − The power efficiency, the physical mechanism of switching, and the efficiency of the electrical detection method for validating the current-induced microscopic switching of the AFM domains are currently under investigation. − Moreover, recent work based on NiO/Pt bilayer devices revealed a current-induced purely thermomagnetoelastic switching mechanism …”