Parametric resonance in a nanowire spin Hall device

Parametric resonance is a versatile tool for excitation of spin waves in nano-magnonic devices. Here we present a joint theoretical and experimental study of parametric resonance of magnetization in nanowires made from bilayers of Pt and Permalloy (Py). In this system, damping of spin waves in Py can be tuned via antidamping spin Hall torque arising from electric current in the Pt layer. We report parametric excitation of spin waves driven by microwave current applied to the nanowire, and tuning of the resonance propertied by direct current. Under magnetic field applied perpendicular to the wire axis, we observe parameter excitation of two types of spin wave eigenmodes: bulk and edge modes. Comparison of our theoretical description of parametric resonance of these modes to the experimental data reveals important role played by the Oersted field produced by ac and dc currents for the excitation process. Theoretical analysis of the data allows us to extract information on the spin Hall efficiency in the Pt/Py device as well as on damping parameters of the excited spin wave modes.