Perpendicular standing spin waves in AuPt/GdFeCo induced by spin-orbit torques

Ferrimagnetic materials provide a versatile platform for high-frequency spintronic devices, combining the fast magnetic dynamics of antiferromagnets with the efficient electrical control characteristic of ferromagnets. Although the GdFeCo films studied here exhibit ferrimagnetic composition, their spin dynamics in the present regime are effectively ferromagnetic, enabling robust excitation of quantized spin-wave modes within a single layer. Here we show that spin–orbit torques generated from an adjacent AuPt layer induce perpendicular standing spin waves in GdFeCo, with resonant modes observed up to the third order. The incorporation of a Ta capping layer serves as an effective antioxidant barrier, preserving magnetic uniformity, enhancing interfacial pinning, and enabling the formation of higher-order modes. In contrast, uncapped films exhibit oxidation-induced degradation that suppresses spin-wave confinement. These findings elucidate the microscopic origin of interfacial control in ferrimagnetic dynamics and provide essential design guidelines for developing energy-efficient, high-frequency spintronic memory and logic architectures. Ferrimagnetic materials offer a promising platform for fast and energy-efficient spin dynamics in next-generation spintronic devices. Here, the authors experimentally demonstrate spin–orbit-torque-driven perpendicular standing spin waves in AuPt/GdFeCo and identify the Ta capping layer as a crucial antioxidant barrier that enhances interfacial pinning and stabilizes higher-order spin-wave modes.