Non-magnetic Origin of Spin Hall Magnetoresistance in Pt films and Epitaxial NiO/Pt bilayers

Recently, electrical control of the magnetic order in antiferromagnetic insulators (AFIs) with a Pt overlayer as a spin current source has been a subject of great interest [1-4], as it allows for ultra-low power control of the magnetic order. However, the detection and nature of purely AFI magnetoresistive switching remains elusive [5-6]. Here, we show that the Pt signal has a strong bias due to the device-dependent current distribution and subsequent electromigration. We determine the effect of current density and magnetic layer thickness on the spin Hall magnetoresistance magnitude and signal shape of both Pt films and NiO(111)/Pt bilayers grown on sapphire substrate. The signal in both materials has a strong temperature dependence, and an exponential dependence on current, indicating the presence of thermally activated mechanisms. We suggest that more sophisticated techniques that directly probe the magnetic order are required to infer information about the AF magnetic state in such systems.
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[2] Moriyama, T et al. Sci. Rep. 8, 14167 (2018).
[3] Baldrati, L et al. ArXiv:1810.11326 (2018).
[4] Gray, I et al. ArXiv:1810.03997 (2018).
[5] Cheng, Y et al. ArXiv:1906.04694 (2019).
[6] Zhang, P et al. ArXiv:1907.00314 (2019).