Abstract
A dynamical spin injection based on the ferromagnetic resonance in a ferromagnetic/nonmagnetic bi-layered structure, is a powerful mean for generating and manipulating the spin current. Although the mechanism of the dynamical spin injection is mainly attributed to the spin pumping, the detailed mechanism and the quantitative understanding for related phenomena are still controversial. As an another important contribution to the dynamical spin injection, the heating effect due to the resonant precessional motion of the magnetization is pointed out recently. In order to quantify the contribution from the heating effect, we here investigate the dynamical spin injection in a CoFeB/Pt/CoFeB trilayer. Although the contribution from the spin pumping diminishes because of the symmetric spin injection from the upper and lower interfaces, a significant inverse spin Hall voltage has been clearly observed. We show that the observed voltage can be quantitatively understood by the thermal spin injection due to a heating effect during the ferromagnetic resonance. A proper combination between the spin pumping and the heat-flow control in the multi-layered system is a key for the efficient dynamical spin injection.
Highlights
A dynamical spin injection based on the ferromagnetic resonance in a ferromagnetic/nonmagnetic bi-layered structure, is a powerful mean for generating and manipulating the spin current
The mechanism of the dynamical spin injection is attributed to the spin pumping, where the excess spins in the FM due to the ferromagnetic resonance (FMR) spill out into the adjacent nonmagnetic heavy metal (HM)[20–22]
Since the dynamical spin injection is mainly evaluated by measuring the inverse spin Hall effect (ISHE), it is difficult to distinguish the dominant contribution in the dynamical spin injection
Summary
A dynamical spin injection based on the ferromagnetic resonance in a ferromagnetic/nonmagnetic bi-layered structure, is a powerful mean for generating and manipulating the spin current. The mechanism of the dynamical spin injection is mainly attributed to the spin pumping, the detailed mechanism and the quantitative understanding for related phenomena are still controversial As an another important contribution to the dynamical spin injection, the heating effect due to the resonant precessional motion of the magnetization is pointed out recently. We have developed an effective device structure for the quantitative evaluation of the dynamical spin injection[27] In this method, the spin-rectified voltage caused by the charge current directly flowing in the ferromagnetic layer can be minimized by using a thick Cu electrode, leading to the quantitative analysis of the dynamical spin injection. By controlling the temperature gradient due to FMR heating effect, we clarify the importance of the thermal spin injection
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