Parametric resonance of spin waves in ferromagnetic nanowires tuned by spin Hall torque

We present a joint experimental and theoretical study of parametric resonance of spin-wave eigenmodes in Ni80Fe20/Pt bilayer nanowires. Using electrically detected magnetic resonance, we measure the spectrum of spin-wave eigenmodes in transversely magnetized nanowires and study parametric excitation of these eigenmodes by a microwave magnetic field. We also develop an analytical theory of spin-wave eigenmodes and their parametric excitation in the nanowire geometry that takes into account magnetic dilution at the nanowire edges. We measure tuning of the parametric resonance threshold by antidamping spin Hall torque from a direct current for the edge and bulk eigenmodes, which allows us to independently evaluate frequency, damping, and ellipticity of the modes. We find good agreement between theory and experiment for parametric resonance of the bulk eigenmodes but significant discrepancies arise for the edge modes. The data reveal that ellipticity of the edge modes is significantly lower than expected, which can be attributed to strong modification of magnetism at the nanowire edges. Our work demonstrates that parametric resonance of spin-wave eigenmodes is a sensitive probe of magnetic properties at edges of thin-film nanomagnets.

Automated summary

We conducted a joint experimental and theoretical study on the parametric resonance of spin-wave eigenmodes in Ni80Fe20/Pt bilayer nanowires. The spectrum of these eigenmodes in transversely magnetized nanowires was measured using electrically detected magnetic resonance, and their parametric excitation was investigated by a microwave magnetic field. An analytical theory taking into account magnetic dilution at the nanowire edges was developed to describe the spin-wave eigenmodes and their parametric excitation in the nanowire geometry. Our findings show good agreement between theory and experiment for parametric resonance of certain eigenmodes, but significant discrepancies were observed for the edge modes. It was discovered that the ellipticity of the edge modes was lower than expected, which could be attributed to strong modification of magnetism at the nanowire edges.