  We investigate magnetization dynamics in a spin-Hall oscillator using a
direct current measurement as well as conventional microwave spectrum analysis.
When the current applies an anti-damping spin-transfer torque, we observe a
change in resistance which we ascribe to the excitation of incoherent exchange
magnons. A simple model is developed based on the reduction of the effective
saturation magnetization, quantitatively explaining the data. The observed
phenomena highlight the importance of exchange magnons on the operation of
spin-Hall oscillators.

Mesoscale and Nanoscale Physics;Materials Science