Tuning exchange-dominated spin-waves using lateral current spread in nanocontact spin-torque nano-oscillators

We present an efficient method to tailor propagating spin waves in quasi-confined systems. We use nanocontact spin-torque nano-oscillators based on NiFe/Cu/Co spin-valves and study the ferromagnetic and spin-wave resonances (FMR and SWR) of both layers. We employ homodyne-detected ferromagnetic resonance spectroscopy, resembling spin-torque FMR, to detect the magnetodynamics. The external field is applied in-plane, giving a parallel configuration of the magnetic layers, which do not provide any spin-transfer torque. Instead, the excitation is caused by the Oersted field. By varying the thickness of the bottom Cu electrode ( t Cu ) of the devices, we tune the current distribution in the samples, and thereby the Oersted field, which governs the spin wave characteristics. Both the average k-vector and the bandwidth of the SWR increases as t Cu increases.