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We study spin torques in RuO₂/Permalloy bilayers grown on TiO₂ substrates by second-harmonic Hall and spin-torque ferromagnetic resonance techniques [1]. Epitaxial RuO₂ films exhibit a strong out-of-plane damping-like torque (OOP-DLT) that is anisotropic as a function of the orientation of current flow relative to the RuO₂ crystal axes. This OOP-DLT is absent in similarly prepared IrO₂/Permalloy samples despite the fact that RuO₂ and IrO₂ possess similar crystal structures [2]. This suggests that the recently-discovered antiferromagnetism in RuO₂ [3] provides the symmetry breaking that allows the OOP-DLT [4]. We also observe a sizable in-plane damping-like torque originating from RuO₂.

[1] arXiv:1801.09636
[2] arXiv:2006.04365
[3] PRL 118, 077201 (2017)
[4] arXiv:2002.07073