Spin-relaxation modulation and spin-pumping control by transverse spin-wave spin current in Y₃Fe₅O₁₂

Heat-current-induced manipulation of spin relaxation in Y ₃Fe₅O₁₂ under an in-plane temperature gradient is investigated. We show that the linewidth of the ferromagnetic resonance spectrum, i.e., the spin relaxation, in an Y₃Fe₅O ₁₂ film increases or decreases depending on the temperature-gradient direction and that this modulation is attributed to the spin-transfer torque caused by a thermally induced transverse spin-wave spin current in the Y ₃Fe₅O₁₂ film. The experimental results also show that the spin-current magnitude generated by spin pumping in an attached Pt film is inversely proportional to the square of the modulated Gilbert damping constant, consistent with a phenomenological spin-pumping model.