Magnetic Field Orientation-Dependent Modulation of Thermal Magnon via Spin–Orbit Torque

Manipulation and amplification of spin waves are critical for developing magnonic networks, which are promising for next-generation data processing technologies. Here, we investigate the influence of the pure spin current on the thermal magnons in a 10-μm-wide and 40-μm-long Permalloy (Py)/Tungsten (W) bilayer microwire system, focusing on its impact on the magnetic damping as a function of the angle between the direction of the applied DC current and the external magnetic field. The magnon intensity has been directly measured using the microfocused Brillouin light scattering technique. A 20 mA current applied along the microwire length (in the positive direction) through the heavy metal layer results in a 26% increase in thermal magnon intensity and a line width reduction from 1.3 GHz (0 mA) to 1.0 GHz (20 mA), indicating suppressed magnetic damping with current. The dependence of integral intensity on DC current indicates an enhanced magnon population driven by spin current-induced damping modulation via spin–orbit torque. In addition to current magnitude and polarity, the angle (φ) between the current and external magnetic field critically influences spin-wave damping and amplitude. Upon changing the angle from 0° (field applied along the direction of the DC current) to 90° (field applied perpendicular to the direction of the DC current), at 20 mA current, the line width decreases linearly from 1.7 to 1.0 GHz. Furthermore, the relative difference in line width between the spectra at +20 mA and −20 mA is 7% at 0°, which increased to 26% at 90°. These results have potential implications for the development of complex magnonic circuits.