Full Control of the Spin-Wave Damping in a Magnetic Insulator Using Spin-Orbit Torque

Abstract : It is demonstrated that the threshold current for damping compensation can be reached in a 5  μm diameter YIG(20  nm)|Pt(7  nm) disk. The demonstration rests upon the measurement of the ferromagnetic resonance linewidth as a function of Idc using a magnetic resonance force microscope (MRFM). It is shown that the magnetic losses of spin-wave modes existing in the magnetic insulator can be reduced or enhanced by at least a factor of 5 depending on the polarity and intensity of an in-plane dc current Idc flowing through the adjacent normal metal with strong spin-orbit interaction. Complete compensation of the damping of the fundamental mode by spin-orbit torque is reached for a current density of ∼3×1011  A⋅m−2, in agreement with theoretical predictions. At this critical threshold the MRFM detects a small change of static magnetization, a behavior consistent with the onset of an auto-oscillation regime