Spin-torque skyrmion resonance in a frustrated magnet.

The frustrated FeSn magnet is technologically attractive due to its extreme-temperature skyrmion stability, large topological Hall effect, and current-induced helicity switching attributed to a self-induced spin-torque. Here, we present a current-driven skyrmion resonance technique excited by self-induced spin-torque in FeSn. The dynamics are probed optically in a time-resolved measurement enabling us to distinguish between the excited modes. We find that only the breathing and rotational counterclockwise modes are excited, rather than the three modes typically observed in Dzyaloshinskii-Moriya interaction-dominated magnetic textures. When a DC current is passed through the crystal, the skyrmion resonance linewidth is modulated. Our micromagnetic simulations indicate that the linewidth broadening arises from an effective damping-like spin-orbit torque. Accordingly, we extract an effective spin Hall conductivity of . Complementary planar Hall measurements suggest a small yet finite contribution of the real-space spin texture in the electronic transport in addition to a primary -space contribution. Our results bring new insights into the anisotropic nature of spin-torques in frustrated magnets and to the possibility of using the skyrmion resonance as a sensor for spin currents.