An effective detection structure for a dynamical spin injection in a ferromagnetic/nonmagnetic metal bilayer has been developed. We demonstrate a clear detection of a highly symmetric signal, indicating a significant suppression of spurious signals due to the galvanomagnetic effects from the ferromagnetic layer. The angular dependence of the signal amplitude assures that the observed signal is caused by the inverse spin Hall effect due to the dynamical spin injection. We also find the importance of the eddy current that induces spin-rectified signals from a ferromagnetic layer.

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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.

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We experimentally investigate the influence of the pressure on the spin-charge conversion efficiency in a CoFeB/Pt bilayer system by using a specially designed pressure-cell setup. The dc voltage spectra under the dynamical spin injection is found to show the systematic increase with increasing the pressure. These modifications can be understood by the enhancement of the spin-charge conversion efficiency due to the modulation of the spin-orbit interaction and/or the interface transparency. The present demonstration indicates that the pressure provides a tunable functionality for the physical constants in spintronic devices.