Evidence for ideal memristive functionality in ferromagnet/antiferromagnet nanostructures revealed by spin Hall effect-driven harmonic measurements*

Viscous dynamics was suggested to enable ideal memristive functionality in neuromorphic applications [1]. However, nanodevice implementation requires efficient electronic driving and sensing of viscous dynamics, which have not yet been realized. We study thin-film Pt/Permalloy(Py)/CoO nanostrips to demonstrate the possibility to drive viscous magnetization dynamics of Permalloy by the current-driven spin Hall effect in Pt and the Oersted field and detect it using the anisotropic magnetoresistance. We utilize ac current driving and detection at the second harmonic produced by mixing between ac current and resistance oscillations due to magnetization oscillations. The viscous dynamics is signified by a large imaginary part of the dynamic response at temperatures somewhat above the onset of exchange bias, consistent with the viscous dynamics of the correlated spin liquid state in CoO recently demonstrated for CoO/Py bilayers by the transverse ac susceptibility technique [2]. Our approach is amenable to downscaling and to efficient ideal memristor implementations.
[1] G.X. Chen, S. Ivanov, S. Urazhdin, APL 117, 103501 (2020)
[2] S. Urazhdin, W. Li, L. Novozhilova, JMMM 476, 75-85 (2019)