Dynamical Spin Injection Based on Heating Effect due to Ferromagnetic Resonance

Dynamical spin injection based on the ferromagnetic resonance is an attractive and powerful method for generating and manipulating the spin current. To date, in a ferromagnet/nonmagnet bilayer system, the spin-pumping effect from the ferromagnet into the nonmagnet has been considered only as the mechanism of the dynamical spin injection. Here, we examine another method for the dynamical spin injection based on the heating effect due to the ferromagnetic resonance in a (Co,Fe)B/Pt bilayer system. The (Co,Fe)B film heated by the ferromagnetic resonance produces the temperature gradient across the (Co,Fe)B/Pt interface, resulting in the thermal spin injection from the (Co,Fe)B layer into the Pt film. The obtained electrical signal clearly shows the spin Hall signature and exceeds 20 mV Ω-1 m-1, which is relatively large compared to the values reported in similar bilayer structures driven by spin pumping. The structural dependence of the inverse spin Hall signal and its power dependence provide consistent results with the dynamical thermal-spin-injection model due to the ferromagnetic resonance.