Systematic study of nonmagnetic resistance changes due to electrical pulsing in single metal layers and metal/antiferromagnet bilayers

TL;DR

This study systematically investigates how electrical pulsing affects resistance in metal and metal/antiferromagnet bilayers, revealing thermal and electromigration effects that can mimic magnetic switching signals.

Contribution

It provides a comprehensive analysis of nonmagnetic resistance changes due to pulsing, clarifying their origins and offering guidelines to minimize artifacts in antiferromagnetic switching experiments.

Findings

Resistive changes depend on pulse amplitude, length, device size, and substrate thermal properties.

No evidence of antiferromagnetic domain switching was observed in NiO/Pt devices.

Resistance variations are mainly due to thermal effects, electromigration, and device training phenomena.

Abstract

Intense current pulses are often required to operate microelectronic and spintronic devices. Notably, strong current pulses have been shown to induce magnetoresistance changes attributed to domain reorientation in antiferromagnet/heavy metal bilayers and non-centrosymmetric antiferromagnets. In such cases, nonmagnetic resistivity changes may dominate over signatures of antiferromagnetic switching. We report systematic measurements of the current-induced changes of the transverse and longitudinal resistance of Pt and Pt/NiO layers deposited on insulating substrates, namely Si/SiO$_2$, Si/Si$_3$N$_4$, and Al$_2$O$_3$. We identify the range of pulse amplitude and length that can be used without affecting the resistance and show that it increases with the device size and thermal diffusivity of the substrate. No significant difference is observed in the resistive response of Pt and NiO/Pt devices, thus precluding evidence on the switching of antiferromagnetic domains in NiO. The variation of the transverse resistance is associated to a thermally-activated process in Pt that decays following a double exponential law with characteristic timescales of a few minutes to hours. We use a Wheatstone bridge model to discriminate between positive and negative resistance changes, highlighting competing annealing and electromigration effects. Depending on the training of the devices, the transverse resistance can either increase or decrease between current pulses. Further, we elucidate the origin of the nonmonotonic resistance baseline, which we attribute to training effects combined with the asymmetric distribution of the current. These results provide insight into the origin of current-induced resistance changes in metal layers and a guide to minimize nonmagnetic artifacts in switching experiments of antiferromagnets.